Yes I believe you are correct. But since the MM is backwards compatible with Black Flag that shouldn’t be necessary. But I bet updates are also made to the CC and ToB 1-3 next. After all the world book already appears to be revised. It is just the inevitable creep of revision and re-release. I just think this is the beginning all these 5E look alike beings lightly different making using them together just a little bit more laborious.I'm guessing it is the replacement MM, not something that obviates their Tomes. They have said their back catalog is going to be compatible.
I own a lot of 3PP 5E stuff but if they are all different I may just head to OneD&D.