> Imagine a user chooses "Sort by rating", and they subsequently observe an item with an average 4.5 ranking above a score of 5.0 because it has a higher Wilson score. Some portion of users will think "Ah, yes, this makes sense because the 4.5 rating is based on many more reviews, therefore its Wilson score is higher." and the vast, vast majority of users will think "What the heck? This site is rigging the system! How come this one is ranked higher than that one?" and erode confidence in the rankings.
It also erodes confidence in ratings when something with one fake 5 star review sorts above something else with 1000 reviews averaging 4.9.
I think you're mainly focusing on the very start of a learning curve, but eventually people get the hang of the new system. Especially if it's named correctly (e.g. "sort by review-count weighted score").