Gammadoodler
Hero
Kinda yeah. It at least means that the only virtue achieved by resemblance to real-world normal is convenience.Then normal means nothing. Trees exploding into fireballs. Cows are violent carnivores. Dogs speak common and cats can fly. Fantasy means no rules. Anything can happen. The sky is purple. My sister has fifteen eyes. You can't tell me what isn't normal!
I'd rather every fighter be born with the blood of Gods than have normal be meaningless.
Fortunately, though fantasy may mean no rules, game mechanics are rules.
And the PHB contains the descriptions of the game mechanics for PCs. So you can be confident that the limitations for fantasy creature PCs, mundane, magical, or otherwise, will be covered by the game mechanics described in the PHB, whatever those mechanics may be.
Further because the PHB is a player-facing document, you can be confident that players will be aware of their characters' limitations, so there is no incremental burden on the DM to highlight such things.