Nah - sorry, it's nothing to do with the basing size, it's the fact that we are talking about rigid square things butted up against each other, which when wheeled will by their physical nature interpenetrate, the size just makes a difference in how far they interpenetrate. It will be the same proportion of their depth that interpenetrates regardless.
And I'm sure in real life that two lines overlapping as I said (10mm = 1/16 of a battalion frontage = very roughly 20 files for a 640 man battalion in 2 deep line) would quite happily have the ability to contract, bend etc. to get past each other as well.
So my point is you can't claim the wheeling is a special case - there are loads of situations where our rigid toys are going to have marginal interpenetrations where in real life they would just squeeze past each other, and people just have to be reasonable about it because writing rules for when you have to test would be a nightmare.
Personally I'm quite flexible (pun completely intentional) about it because it drives me nuts to have pedantic details get in the way of a good game :-)
Although I'm also not completely happy about people throwing masses of columns about shoulder to shoulder - what is that, some sort of phalanx? :-)