So if I’m understanding you, because towing the bike in neutral is like a constant deceleration (possibly for hundreds or thousands of miles), the rear bevel bearing is taking a load that’s opposite to its intended use, which wears it rapidly.
However ! I once towed my mates BMW GS 650 to wales and I think it some how dropped into gear and fused the 2nd gear ! cost me 1500 quid to get fixed with full engine rebuild !
so make sure your in neutral and the bike does not jump easily into gear (i.e. check regularly on route)