If you think about, more and more 29er bikes out there, most are running discs and 15mm through axle, so it makes that part instantly transferable. Never needed to release a front wheel in a hurry in a cross race, unless you have a spare set of wheels in the pits, it’s a bit of a pointless argument, as if you are running a spare might as well run a bike as there are so many other things that can/could go wrong. It makes more sense to buy a pair of reasonable medium bikes, rather than just one top end bike. For those that know me, I only came to this thought too late, but it is nice to have a top end bike to play on, so far one puncture and a snapped pedal, neither would have been affected by a through axle.