I got around to using the creative grass blocks my self finally, and they kinda suck. If you add them to another chiseled block, they get a horrible orange color. So yea, mine is still better despite its flaws.

(I noticed people are still downloading this little mod, so I'm adding this warning. The grass block added to the creative menu in 1.18 is far better than my attempt is. I plan to revisit this mod and create a recipe for that creative block, but truth be told I probably will not do so till I myself get to the point I again need chisel able grass blocks)

Downsides 

It does not change color with the seasons or biomes, so it will never match the surrounding exactly. Thanks to Tels I got this to work, but as soon as I added this ability it stopped being chisel-able. Haven't given up yet, but this may prove impossible.

Upsides

fixes a problem where grass blocks half under another block revert to dirt, leaving dirt patches at the edges of your builds.

Allows you to combine a grass block with something else, so you can have cleaner or diagonal edges on paths or retaining walls.

Allows you to have grass in an oasis in the desert biomes, since grass will not grow on dirt in those biomes. And many others I’m sure you will think of. 

To-do list

Continue trying to fix collar change problem.

Add a chisel-able path block (will try to retain walk speed buff) but no promises.

Lastly, if anyone with more skill wishes to take this idea and do it right. You have my very best wishes. All I ask is publish it so I can have It too.