This issue seems to be happening because the REST API endpoint preloading is somehow satisfying the enqueues, meaning they don’t happen to the block editor itself.
As a quick fix, something like this will work:
[Removed – see updated code further down]
But this might be a bit of a sledgehammer approach to solving the issue, but I wanted to get something over to you as soon as possible for those who wanted to stick on WP5.9.1
We’ll keep digging into this though, and give a further update shortly.
