So far (knock on wood) it hasn't happened to me, at least on a hunt such as you are considering. This is a pretty much standard policy among a bunch of outfitters worldwide. Should it scare you? Perhaps. At least it makes you a bit more careful. You are right that if you hunt long enough it probably will happen.
My short and skinny take on the subject is that if you want to hunt the big ones, say like in Saskatchewan or Alberta, you accept that as part of the game. Go and enjoy the hunt. Think positive thoughts, and make your shots good ones.
Now, you want to talk pucker factor? In 2003, I hunted Cape buffalo in Africa. The trophy fee for a buff was $10,000 back then, and my first shot was not a great one (there is more to the story). We managed to get the buff, but had we not, I was out ten grand. Now that sort of money will tend to shrink the old sphincter. Please note that as evidenced by the following photo, the buffalo is the one on the wall. Had we not recovered him, I might be in that location due to one very upset W 1 FE unit.