For what it's worth, no phone running iOS (and I think none running Android either) has landscape mode enabled in the launcher or the system settings. I would guess Apple and Google have both done a considerable amount of testing in this regard and found that below a certain screen/device size, landscape mode in these areas is just not something that makes sense (and I could see why).

Edit: that said, I agree there are some inconsistencies that should be fixed (or: should have been fixed long ago), but Jolla clearly prefer to put their UI team to work on creating unwanted, unnecessary and ugly changes to the cover designs of their applications instead of doing 1-line fixes.