Consider this:

The Viera are, in spirit, the propriety of Ivalice and under the guiding hand of Matsuno.
Yoshi and Matsuno are friends, and Yoshi brought Matsuno on board to guide the Return to Ivalice arc, and ensure it remains faithful to Ivalician lore.
So it makes sense that Yoshi would respect Matsuno’s creations as his to have the final say on.
Ivalician lore states that male Viera are so rare, that no non-Viera has ever seen them. To go against this would not merely be breaking FFXIV lore but Ivalice lore too, and in all likelihood, they may think that if male Viera were to ever be revealed it should be in an Ivalice title, not in what essentially amount to a fanservice a cameo in an MMO. It would basically be FFXIV stealing Ivalice’s thunder.

So, how about they get around this, by introducing a FFXIV unique race, who in FFXIV lore are related to the Viera, but this does not step on the toes of Mastuno’s Ivalice.
This new FFXIV exclusive race, related to Viera, are predominantly male, or are entirely non-dimorphic/asexual, but look masculine.
This new race are called the Hrothgar, they’re large, hare-like people, with manes instead of tails.