To help future optimizations for given quantizations, we have been trying to limit the quantizations to ones that fit for majority of users.
In the case of mistral-small3.1, Ollama supports ~4bit (q4_k_m), ~8bit (q8_0) and fp16.
https://ollama.com/library/mistral-small3.1/tags
I'm hopeful that in the future, more and more model providers will help optimize for given model quantizations - 4 bit (i.e. NVFP4, MXFP4), 8 bit, and a 'full' model.