This would also help me,
With BiSS-C I would be able to select an appropriate encoder for my desired setup (17+ bit resolution required)

There's a post I found where someone was supposedly able to "read" a BiSS-C encoder with SPI in the "SimpleFOCproject" community forum. (can't post links yet, but search for SPI BiSS-C SimpleFoc and it'll likely come up. )

I would also benefit from being able to read the encoder directly.

My system does not work for Closed loop (no encoders have enough counts to be 2x+ my full step counts) but would like to implement meta commands with loops checking for acceptable range of encoder ticks since last referenced. Essentially exactly what M569.3 would provide.