the theoretical reason for doing that is that if you have to split jamming power over broader frequency range, then for every n^2 times increase in bandwidth, here number of channels, range decreases n times. however gnss signals are so weak, it probably doesn't matter, and if you're adding extra power per channel, then it doesn't apply

now if missile detects that gnss is fucked with (signal too strong, wrong direction, physically impossible location), the correct thing to do would be to fallback to inertial navigation while accepting that accuracy decreases until gnss can be received again, if at all, and acted upon. theoretically speaking, it's a matter of software update, better hardware also can help with that, so idk why would they release this. maybe there's something that prevents this