I tried reading everything and am not seeing this but might just be missing it. I'm finding that if a ride goes down and I am assigned an anytime FPP (usually of similar rides), that it is independent of my other FPP's for the day. So if I'm at MK and Pooh goes down, I get an email telling me I can ride similar rides (IASW, UTS, Pooh, etc.) at any time of day. However, I can then immediately book another FPP for any ride via
MDE, even if I haven't used that one (or other remaining ones) yet. The "replacement" FPP acts as a "bonus", not an actual replacement. I figure if I'm just realizing this that others may not know as well - I swear this wasn't the case before the changes in April.
One thing I don't know is whether this happened with a Tier 1 ride at Epcot or HS if you could then try for another Tier 1 ride or if it would limit you to Tier 2's since your replacement would most likely be a Tier 1. I just haven't had a Tier 1 go down on me since I've been checking this (despite having FEA 3 times this week strangely enough!). Anyone experienced this?