This was pretty much all the culls:

It definitely is more like dehydration than rot. The spots are all dry and tough like jerky, vs mushy. I wasn't really thinking purple when looking at them, but perhaps the earlier stages are more purplish. I wish I would have noticed sooner, but they were mostly on the upper facing sides. Only when one branch got bent down due to the weight did I spot it and then pulled out the ladder to check them all.
Purple spot gives a lot more google hits, so hopefully I can fix my practices. This study suggests a correlation with night temperature,
https://www.researchgate.net/publication/248478075_Purple_spot_in_loquat_Eriobotrya_japonica_Lindl_is_associated_to_changes_in_flesh-rind_water_relations_during_fruit_development, which has been pretty low. Even if we recently have been hitting 70s in the day, it's still been 30-40s at night. Plus, it mentions elevated sugar levels affecting the osmotic balance, and the sugar changes kick in mostly around color break. Also, thinning increases the risks and I did a little of that this year to see how big some can get. Like this study found incidence increases with increasing leaf area to fruit ratio:
https://www.cabi.org/isc/abstract/20043000289. Some studies suggest supplements (Ca/N) prior to color break, so perhaps I should be feeding earlier, but not sure on that part yet. Conversely, could recent rains have diluted levels, particularly since I have very sandy soil.
The variety is Champagne, but there are a couple of Kaz's Big Jim and some of those fruit were also affected. I don't see any spots on leaves. Just some occasional tips and some burnt margins on tender growth.