It’s not about us embracing them, it’s about them embracing the protocol, which they can do whether we stay federated or not.

The argument against defederation is that it tells newcomers that the defederated instance is an island and they’re better off joining the place where they can talk to their friends. Meta can more easily extend if we’re not around to explain why extending is a bad thing, and if we’re not around to advocate for people to ditch Meta’s platform and join an open one

Here is what it actually means

Embrace: Development of software substantially compatible with a competing product, or implementing a public standard.

Extend: Addition and promotion of features not supported by the competing product or part of the standard, creating interoperability problems for customers who try to use the "simple" standard.

Extinguish: When extensions become a de facto standard because of their dominant market share, they marginalize competitors that do not or cannot support the new extensions.