I think alioopla is expressing reasonable frustration with an issue that is a big time waster for a lot of users.
Apparently alioopla has some other things going on, but the basic issue discussed here is that iOS Mail is not being marked as read after many users read their mail, and alioopla is experiencing the same thing.
People are looking at their mail on an iOS device, but they have to manually mark mail as read.
I've confirmed this on multiple users' devices, under multiple versions of the OS from 13 through 14, including some users who only have a single device with a single Apple mail account, and others who have more than one mail account and share mail across devices from mobile to desktop.
In every case I've seen, if the mail is read on desktop Mac Mail, the mail is correctly marked as read and then all mobile devices also mark it as read. But, if the mail is read on the iOS device, it does not mark as read. So it would appear that this is an iOS issue.
So, whatever the technical underpinnings, for many users, when they use the app normally as expected, they're not getting their mail marked as read as they would normally expect. Whether this is a bug, a design issue, or an intentional part of the feature set, it's clearly a problem for a lot of people and hasn't been resolved.
If anyone has a clear and simple solution, that's great. But no luck so far.