Even for client software it is bad - an app quitting out from under me because it wants to update is functionally equivalent to a crashing bug - but they're offering daemons this way, which is just insane.
Who doesn't want all their containers randomly restarting because someone up the distro chain decided when your machine needed to upgrade?
The cluster will not come up because your down node is now not the same version as the other cluster nodes.
This doesn't happen, at least on account of Snap. It's copy-on-write when it comes to updates, and whatever version you have running at the time of update will happily keep on running. I've been mildly confused by this a couple times, when I would end up with two different versions of VS Code running side by side, but the bright side was that my work wasn't interrupted.
It incidentally also sidesteps all the problems that stem from libraries or configuration being updated under a running application, which can happen with Apt.