Looking at the documentation time and again, it seems like the offset doesn´t get wrapped at all(Just checked against limit, which will always fail on a 286+ when over the limit(in the descriptor), pun intended). Thus even in Virtual 8086 mode(which is a protected mode version of real mode), addressing over 64KB causes a #GP fault, because it's breaking the limit. No wrapping on the offset is thus needed.

One thing I'm wondering about, though:
with expand-down descriptors, with 16-bit offsets(which may or may not overflow), it doesn't cause problems(because the high 16 bits are always set, thus making the modulo 64K effective still)?