Begging his pardon even so, but there is a unavoidable dichotomy between the Smith who sits comfortably in the familiar surroundings of Kingsholm talking about his life in (mainly Gloucester) rugby and the Caledonian alter ego who has done Five Nations rugby a service by blazing a trail on behalf of an endangered rugby species called the open-side flanker.
At nearly 32, Smith has been around long enough - more than 350 Gloucester games since making his debut as an 18-year-old - and dealt with enough aggravating inquisitors to know that curiosity about his provenance will continue as long as his Scotland career. "I get so irritated that people keep dragging it up," he complained. Sorry, Ian, but there is no escape.
"I know it's a fact of my past but it does get annoying when people harp on about it when they could be concentrating on the rugby or the game. There is nothing I can say that will make people think I'm a Scotsman. All I can do is go out and play, and if you think I play like an Englishman playing for Scotland, then so be it. The fact is I feel like a Scotsman and always have since I was a young boy."
But the fact is, too, that under present eligibility rules Smith would have committed himself to England - at least until a decent interval had passed - when he represented England B against Spain in 1989, and it is not widely remembered that in 1990 he was even in England's preliminary squad for the '91 World Cup.
But it was in 1990, on the very day that he dashed away from a Gloucester game at Nottingham for one of those England sessions, that the change of allegiance began to occur. Gloucester's defeat that day cost them the championship, but the consolation for Smith was a conversation he had before his departure with Chris Gray, the Nottingham captain.
Gray, an exile from the Lothians who had played in the Scotland second row against England when the Grand Slam had been won six weeks earlier, knew of Smith's Scottish connection and, as any good Scot would, tapped him up. A later phone call from Ian McGeechan, the persuasive Scotland coach, made up Smith's mind up for him; he made his Test debut in 1992 and will win his 16th cap for the land of his paternal grandparents against England this afternoon.
Smith's father Dick, an outstanding Gloucester flanker who appeared in the very first knock-out final at Twickenham in 1972, was Gloucester-born to a couple from Aberdeen which Smith Jnr insists gave him a Scottish allegiance from his earliest years. "I had always supported Scotland as a young boy and I always felt I wanted to switch," he said.
It was England's loss. Ask any back-row forward on the Courage league circuit and he will pay a sincere tribute to Smith's quality, bearing in mind also that he has sustained this individual excellence during a period - ever since that defeat at Nottingham was followed a week later by a cup-final annihilation by Bath - when Gloucester collectively have fallen far short of their traditional eminence.
Which perhaps helps explains why he has flourished in a different, less introspective and claustrophobic environment. In the Scottish chain of command Rob Wainwright, the captain, has this season had the good sense to use Smith, with his wisdom gained from long experience, as his first lieutenant.
And within the thrilling strategy of all-out movement with which Scotland have beaten Ireland, France and Wales, Smith as open-side flanker has more than any individual been responsible for its successful implementation. To think that not so long ago fleet-footed forwards of Smith's ilk were on the verge of extinction in the international game.
Not that Smith ever accepted its inevitability. "I've always said it: what goes round comes round. When you look at the successful teams, especially New Zealand and Australia, they have always picked a specialist open side and basically revolve the game around him. So it's been frustrating to see a game evolving here that involved big men playing an upright game, hitting up the middle.
"But I was always confident that it was a cyclical thing. Moves we used to use 10 years ago and which then petered out for a while have come back into use again and it's clear that the trend is back in the direction of players like me. But for the open side to be successful depends on the way other units work as well. A back row is only as good as the front five in front of it and the back line behind it."
Wales, with Gwyn Jones, and Ireland, by reinstating Denis McBride, are treading much the same path and even in the home of back-row mastodons, England, they have come to acknowledge the requirement for a specialist such as Smith, even if by choosing Lawrence Dallaglio they designedly have a player who must learn as he goes along.
None, one would suggest, has done it as well as Smith during this exhilarating Scottish season. "It is, quite simply, the natural way for me to play, what I've always done from when I was a young lad years ago," he said. "If I perform as I should, then the side functions as it should, and that's how it will be against England. That's a responsibility, I know, but I feel comfortable with it.
"I play against these blokes in English club rugby week-in week-out, so I know what they are like, what they can do, their strengths and weaknesses. I'm as confident as you can be going into a game like this and that's a deliberately ambiguous statement. If we - or should I say if we are allowed to - play as well as we can, then it could be a great day." A great day for Aberdeen no doubt, but would it be a great day for Gloucester?