To answer my own question for those who may also want to use the Auto Update Client Applications setting in YSE. It was not what I expected, it was better than expected, but with a strange twist.
Shortly after completing the MICC upgrade from 9.1.2.x to 9.3.x and launching YSE, I noticed what appeared to be files copying down. Evidently, the updated files and components are pulled down, no prompts were seen - all silent and behind the scenes.
Spot checking other computers, the same was observed. If the update already had completed, nothing was seen (no files copying down).
As for the strange twist... The Windows 10 Programs and Features did show the updated version installed (9.3.4 in my case), however the install date was not changed. On some computers that date was 2019, 2020, earlier in 2021. If I ran a 'repair' or 'change' and manually completed a reinstall, that install date would then update.
What I expected was a user encountering prompts as if a manual install were taking place. So this did work better and I will plan on using going forward. This will eliminate my need to use SCCM.
Regards.