Apparently, the switch to Meson was approved, and coded, ages ago, but Dolstra kept dragging his heels on it.
For a discussion on this, see https://github.com/KFearsoff/nix-drama-explained/issues/1
> Single-handedly blocking Meson, which has a passed RFC, for five years because he doesn’t know meson but knows his own build system
I don't know about exact timelines, but the letter is definitely wrong about this part.
Apparently, the switch to Meson was approved, and coded, ages ago, but Dolstra kept dragging his heels on it.