That does seem to be more detailed on what the problem is... I don't use realms normally so I couldn't see what else was effected by it. I'm wondering if the way the realms menu is overlayed is effected by monitor size. If that is the case, that could be a contributor to the problem here...
Mojang is doing account migration in batches, the reason why it probably isn't giving you a prompt is because you aren't one of the people in the current batch that Mojang is migrating at the moment.
That does seem to be more detailed on what the problem is... I don't use realms normally so I couldn't see what else was effected by it. I'm wondering if the way the realms menu is overlayed is effected by monitor size. If that is the case, that could be a contributor to the problem here...