Bonus to rolls? Great! Ravine cuts off potential escape? Bad! So it all works out. And it's not like Rey was going to keep backing up anyway. Oh hey, this is probably what the spooky voice was referring to for "hold your ground"! That would have been a heck of a last step to take once the ravine opened. Though this feels like a justification for why Rey stopped moving backwards in the movie rather than being a similar occurrence. I don't recall Force Ghosts previously being able to talk without appearing and either of those could be distracting in the middle of a fight for the audience.

I bet the game reason Pete is getting a bonus to Attack/Parry is the same as why there's now a ravine. It's to make the fight more dramatic for the GM while still keeping it mostly balanced as a fight. Sure, the ravine is probably caused by Allan and BB-8 exploding stuff down below, but it wouldn't necessarily have opened up near the fight. Now Pete can fight a little more effectively and not get sliced up as fast, while Sally has a much better option than "Force Push into a tree" if she thinks of it. Kylo had an excellent strategy when Rey was just using a blaster; why not try again? Force users still can't fly under their own power as far as I know and Rey hasn't been said to be exceptional so far.