It's especially backwards because most extensions worked fine when they were first cut down to that list of 20.

They (the proclaimed bastion of user choice and freedom) just didn't allow you to install them. Forks and self-built versions handled extensions just fine immediately, there was no technical blocker, just managerial. For years. While constantly proclaiming that it was just a brief temporary state.

I switched to some of those forks immediately, literally every extension I used before worked perfectly. None of them were in the blessed list.

I honestly can't see it as anything but an intentional self-harm move, behind a bunch of smoke and mirrors.