Block.getAmbientOcclusionLightLevel() only checks for the block being a full cube and so the result is this.

https://i.imgur.com/wkLrnF3.png

This could be fixed with an additional check in Indigo. But should it be?

(Hat tip to @InsomniaKitten for the find.)

We've already done some AO fixes, no? With a way to toggle between "emulate vanilla", "emulate vanilla for non-Fabric models, fix bugs for Fabric models" and "fix bugs for all models", with that last bit being the default, IIRC. I would just put this "additional check" under the same "fix bugs?" check.

Alright. Is there any supported way to expose configuration options for API yet?

No, but implementing the check in the right place will allow to expose it a bit later.