That sounds kinda weird but at the same time understandable in scalable, worldwide, asynchronous and distributed applications, in that "mark read" is not a data

That sounds kinda weird but at the same time understandable in scalable, worldwide, asynchronous and distributed applications, in that "mark read" is not a database query but a task that gets added to one or more task queues that eventually lead to a data update which in turn eventually leads to a local state change. That said, apps that talk to queue / async based backends like that should employ optimistic updates, that is, mark as read and presume that goes alright, instead of wait for an update. That said, given it's a new architecture, maybe that'll be implemented eventually.