Price protection offered through certain subscription passes is different from price protection offered through Uber Rewards.
Monthly subscriptions provide several benefits, including price protection, which is a varying discount on all UberX and Pool routes in your city for an upfront monthly price.
Uber Rewards is different. Uber Rewards is a loyalty program that is free to join. Benefits for Platinum and Diamond level members include price protection on one, pre-selected route, which means you won't pay more than the protected price on that route, except during extremely busy times when you'll be guaranteed a discount. Members in these levels need to configure their one route to experience the benefit.
If you are both a monthly subscriber and a Platinum or Diamond tier member, you will always see the monthly subscriber Pass pricing.