In the past, I think “device messages” would sync across all accounts if you used more than one account. However I noticed that now it seems that one account is picked at random, and newer device messages only show up for that account. Is this a bug or a feature?
no, “device messages” are not synced across profiles [1] on the same device and have never been.
the idea of “device messages” are to show information that are useful/special for a given profile on that device - they’re generated locally and may contain topics as “your server is low on space” “profile transferred” or “you did not update for a long time, please check for updates” or “what’s new?”
for the sometimes added “what’s new?” message: they are added to profiles only that exist while updating, and are notified only for the last recent profile.
depending on how profiles on the device are used, however, one can get the impression that they’re sometimes in sync 
Delta Chat talks about “Profiles”, not “Accounts”, to not confuse other readers, i stay with this term ↩︎
Thanks for the explanation. This gives me a better understanding of how device messages work.
I found that the “Switch Profile option moved” message, which I assume is a “what’s new?” message, was only added to one of the existing profiles while updating, though it sounds like it should have been added to all of them and then only notified for the last recent profile.