We're talking about more than one effect here. RT patients are well familiar with the effect of losing the sensation which lets you know if it's solid, liquid, or gas waiting to come out. Your bowel doesn't have nerve endings in it and can't feel what's there, except the last several inches, which is actually formed of normal skin with nerve endings. This is specifically so you can sense the nature of what's waiting to come out, i.e. is it safe to fart? This area is very close to the prostate, and RT usually stops these nerves working for some months, hence being not safe to fart away from the toilet, not knowing what's going to come out. This effect usually recovers though.
I don't know where those nerves run but it may well be that prostatectomy ends up bruising them, creating the same effect hopefully only temporarily.
As for substantial changes in bowel behaviour... With open prostatectomy, I wouldn't be surprised if your bowel might end up slightly rearranged. In a few people, small intestine does come down close (causes issues for RT planning), but I would be more surprised if this is an issue with RALP.