It's not understandable at all.
They used a similar reason for male Miqos and they are in the game if I recall. The one for Male Viera is quite a cop out in my opinion.
They are free to design the game as they want. However as I said I'm not interested in either race. Which is a shame because I'd play a male Viera. And there is a lot of fair criticism on the forums and Reddit right now. Which I hope they at least acknowledge.
As I said it's the only poor thing from that whole keynote. So all in all it was a pretty amazing keynote. I don't mind dancer being a RDPS, the zones are gorgeous, the artwork is incredible and the videos shown off are badass. And I'm still incredibly hyped for the expansion and ready to be a darkboi going around spreading my darkboi musk in the zones.
I've just never liked genderlock classes, races and whatnot. It just feels restrictive as hell in a game that's about offering a bit of freedom. But I will say one thing. All those people saying "FF14 KOREAN MMO" now just lol. I mean yeah I'm not happy about it but some people are blowing it way out of proportion.