I suspect you are right ... kind of
After your reply I tried a few other launchers than the LOS default Trebuchet - some showed the issue, some didn't.
Interestingly I found a few other discussions about other devices and their launchers, going back several years, including about the vanilla Google launcher on Pixel devices where people were having the same issue.
Seems the only `definitive` answer anyone ever got was on one occasion from a Google Fi support-desk droid replying about Android 8 Oreo on Pixel 2 :-
I played around with Trebuchet a bit more, and I *can* get the landscape icon labels to display ... but only if I set display size two steps below default to "Smaller"
This isn't terribly useful, however, as the Display setting scales *all* screen elements globally, including fonts - not very usable.
(Setting Font size, specifically, has no effect on this issue at any screen size setting).
Interestingly, when the screen scaling is small enough for the icon labels to appear the dock bar is also moved from right side to bottom of display.
So ... it looks like another one of those arbitrary UI scaling/rotation annoyances that have plagued Android on tablets since the dawn of time.
It's not really a deal breaker - I didn't bother reporting it here as a `bug` since it doesn't particularly bother me and just assumed it was something to do with me having my Fonts setting as Large.
I just wanted to confirm
xda_lex's finding and let him know he wasn't going mad - it isn't just random weirdness with his install, but a reproducible issue