AFAICS, there is no explicit "backend's default behavior". The mechanism seems entirely controlled by the Artist's draw method (via @allow_rasterization). The backend/renderer only implements start_rasterizing / stop_rasterizing (or not if thy do not support rasterization, which leaves these functions as no-ops).

The only "default" is that pixel-based backends ignore this setting, and vector backends respect it.

Also, it seems that the value of None is never checked explicitly, but we only have a a truthy comparison if self._rasterized. Therefore, we make this a real bool parameter. - Would need to change the default init value as well, which is a non-doc change, and if we wanted to be nit-picky also is an API change, because get_rasterized would return another value. So I leave this for another PR.

I suspect that this wording means "in Agg we _always_rasterize, in svg the default is to emit vector data", i.e. the default value is to do what ever the backend does (at least that is how I have always read).

👍 "backend's default behavior" is still a bit weird wording. To me, "default" implies that one can configure it to something else.

Anyway, the wording is gone. And a possible removal of None is for another PR.