I can back this up. I remember seeing him in the Shed more than once. I'm pretty sure he's a genuine fan, even if he's not been in a while.
Do you remember ITN newsreader Alasdair Burnett? I remember one night in particular. He was reading out midweek scores. He read out, I think it was Meadowbank Thistle's result, then when it came to us, instead of Partick Thistle, he said "THE Thistle!". It's well reported that he was a Jags fan from time spent in Glasgow as a reporter, and made no secret of that when reading our scores out.