When you have increased mining size, breaking grass breaks nearby grass blocks. Going even further - breaking grass blocks breaks nearby obsidian but destroys the obsidian in the process

What AS release version? There's three major versions being tracked on the git at present, and half a dozen sub-versions.

I'm using astralsorcery-1.16.4-1.13.1.jar

It'd also be great if sneaking prevented the size effect taking place and block "hardness" affected mining speed to prevent exploiting this

The hotkey for disabling/enabling perk abilities enables/disables the mining size as well.

1.16.4: Fixed with version 1.13.3

I am now using astralsorcery-1.16.4-1.13.4.jar and breaking normal gras still destroys block around it which is suboptimal imo.
Link to an example: https://gph.is/g/ZY07jd1