You have a point that at scale everybody except maybe Google is using Nvidia. But r/locallama is not your evidence of that, unless you apply your priors, filter out all the hardware that don't fit your so called "hypotheticals and 'testing grade'" criteria, and engage in circular logic.

PS: In fact locallamma does not even cover your "real world use". Most mentions of Nvidia are people who have older GPUs eg. 3090s lying around, or are looking at the Chinese VRAM mods to allow them run larger models. Nobody is discussing how to run a cluster of H200s there.