"there are no "solid clay" chips anymore"
Never was any. Something has to be added to hold the clay together.

"Now, are you saying the formulas for compression and injection chips are exactly the same?"

No, I am not saying that.
I have no clue on the formulas manufacturers use. I doubt any of them will post here and tell us.

I did know at one time what percentage of clay was in a Paul-Son chip when they started production in the mid 60's but it is lost in many years of notes.