Background usage limits

Interestingly that was the only one automatically added in so far, due to "high background usage" (that is, it has a history of it). It seems to me like my phone has applied a different formula of "automatically adding/allocating" various apps compared to other people.

I note at least one of the users in this thread posted that they only noticed 1 app in Sleeping despite having the phone since launch, so I'm not alone.
Yeah it's a couple reason why device care would put apps to sleep.
1. Haven't been used more then 3 days
2. If the app using high background activity

Deep sleep if you haven't touch that app in awhile
 
Yes, I'm yet to get an automatically moved app into sleeping or deep sleeping due to not being used for more than 3 days. Been well over 4 weeks now since last factory reset.

For fun, I've manually added a couple of apps into sleeping in the past few weeks, but then removed them almost immediately. Anyway, I think I'm actually happy with this process, as I prefer to manually control which apps are sleeping, deep sleeping or never sleeping. Probably I should simply disable "Put unused apps to sleep", although I tend to leave these things as default (as you never know what else the function does that helps general optimisation).
 
Just an update - over a month since last factory reset, I get a "warning" that a couple of apps will be put into deep sleep soon.

So it seems the function that I described in the original post is indeed working. It's not very aggressive though, which is a good thing.