Does sundowning coincide that tightly with the actual sun?
It does, yes.
The term is pretty much entirely about the time of day and how almost universal it is for dementia and Alzheimer's patients to have worsening symptoms (and some symptoms that only occur) from late afternoon to early evening. Although it can be fitting and sometimes get used with a bit of that double-meaning in there that has to do with a person being in the later stages of their lifespan, a "sundown" of their life, that's not where the term comes from or what it means. There are plenty of relatively younger patients (like with very early onset Alzheimer's) that have all the usual symptoms of sundowning, like being more easily upset, agitated, even getting uncharacteristically belligerent only around that time of the day/night cycle. Source: used to do volunteer work with Alzheimer's/dementia patients and their families.
If they're not already on hexbear/lemmygrad, they should be. (Also, for those of you who like arguing with libs and don't take much mental damage from it, your comrades in the trenches appreciate it when you join in and back them up. Be that on
or even in the lemmyverse with an .ml account against .world... just sayin')