That's really a stupid expected behavior. LOL So Apple changed it so that you can't back up while sleeping with Silicon Mac unlike in Sonoma? Because in Sonoma it can do that and now in Sequoia PowerNap is disabled for Time Machine to backup? That doesn't make any sense at all. As an experiment I turned off sleep on my iMac M3 and the Time Machine error message didn't come up.
"When your Mac is plugged into a power adapter, Power Nap can also do activities such as downloading software updates and performing Time Machine backups."
I know, it is ridiculous.
Wait, no, it's worse...: Apple silently slipped this "unlock for TM to function" into the documentation, which means they KNEW about this all along. Which is a catastrophe in many ways
- backup is nearly impossible for most of my macs because they cannot remain unlocked all the time (OF COURSE NOT!)
- Apple had hte choice to fix it, but chose to silently roll this into a public release, knowing all the effects; which means: they obviously don't care
- also, since the chose to release it, they obviously do not have a fix for this in the drawer; how can this be, since it has been working for years (well, yeah, most of the time)
All in all, this really stinks.