Your temp-0-vs-sampling split is the cleanest diagnostic in this whole thread.
It separates two failures that look identical from the outside.
One: the determinism trap. Greedy makes the loop a fixed point, re-entered token for token. Sampling breaks it, which is your 12 to 6.
Two: state collapse. At IQ1_M sampling cannot pull it out, because the model has lost the memory that it already ruled this branch out. A random escape just re-converges.
The tell that separates them is lexical. Exact n-gram repeat means determinism, and temperature or a repetition penalty fixes it. Same dead reasoning reworded means the working memory is gone, and nothing short of more bits helps.
So I would split loop rate into those two buckets rather than log it as one number. The ratio is the real bit-depth signal: exact-repeat share should fall and reworded-repeat share should rise as you drop toward 1.7-bit.
The 6 of 25 that survive sampling at 4-bit are already sitting in your prediction files. Do they repeat the exact tokens, or reword the same dead path?