With the new chunk rendering + falsetweaks, Optifine's better grass does not convert the grass correctly. It seems that chunks the player isnt currently in don't swap, and when you walk up, it swaps.

Video demonstrating this below. Note this is when using a texture pack, I'm not sure if this is occuring with vanilla textures yet. Ill try that when I have a few free minutes.

https://youtu.be/aGVNRyvZ9tk

Same issue here.
Grass side overlay also seems not to use the biome's foliage color unless the chunk is updated by placing or breaking a block or moving around:

same problem

still happening as of 2.8.1

edit: it now seems to apply "better grass" to the chunk you load in to, but nothing else.

Does this still happen on 3.5.x?

Ill set up a quick pack to review this tomorrow - I've been working on a shader for angelica the past couple of weeks, so I've been preoccupied.