I think it has more to do with Epic Universe than Monsters. With this delay, they now have the Mermaid show, the Villains show, Starlight, and Test Track 3.0 all opening within the summer 2025 timeframe. I wouldn't be surprised if Zootopia gets pushed back to summer as well to coincide with Dinoland's closure.
Of course, I could be wrong. Perhaps the AC closure combined with actual project delays would necessitate some onerous relocation of backstage facilities that they weren't previously accounting for.
EDIT: Also, if they had already internally decided to get rid of AC, why not spread the good word as soon as possible, and relieve us of the psychic weight of the hypothetical closure of the Muppets Courtyard?