There's a difference between the actual prices being impacted (which I have seen reports happen with Uber rides) and losing promotional discounts which is what the Reddit user experienced and I have personally seen happen with Uber Eats after signing up for Uber One - a restaurant can't manipulate the prices of their food based on if the user is signed up for Uber One or not, but Uber Eats can stop giving you their promotions or at least reduce them once you have Uber One membership.

As a DP, my daughter used to consistently get targeted 50% discounts to her Uber Eats account and used them all the time. At one point she got an offer to sign up for Uber One as a student for a discounted rate and she accepted it. She didn't completely stop getting targeted discounts but never again 50% off. They became 40% off and then 30% off followed by 15% off (which doesn't even cover the increased Uber pricing over in store pricing plus the fees that exist even with Uber One) and then no more promos at all. She is not planning to renew Uber One - doesn't have a Plat card either way and isn't using rides at all and not enough of Uber Eats especially with no discounts anymore.