The leaker never talked about gender locking, but he never confirmed male viera either. Just said viera are coming. Considering viera have only always been depicted by females of the race, it's easy that if you see a female viera it's confirmation viera are coming.

Th gender locking comes into the logistics of developing a new race. It takes a lot of work to make a full blown race, all the art assets with around 7 new hairstyles etc. Adjusting equipment to fit them, and the huge amount of emotes that need to he created for them (and all the other animations rigged to their skeleton).

So when comments leaking of there potentially being a second race, realistically having two full blown male and female races is highly unlikely. That is a TON of work. Yet creating 1 male only race, and one female only race is the more logical option. (This is also why having two very distinct different sub races is also very unlikely because it's just as much work as doing a second race. There are shortcuts such as sharing emotes they could take but it's still a lot of new assets to create, they would be less separate than Hyur differences for example).

Once those are taken into consideration, there's a history of evidence old and current that paint a picture that genderlocked races may indeed be coming. From old comments straight from the director saying he would do exactly that (specifically with viera as well), with new lore setting up to explain why male viera may not be around in any meaningful way, to doing a full race reveal with no mention of male viera coming, even if they were still a work in progress. To then being coy and vague when asked directly about it in interviews, even saying that he sees himself as a contrarian when an interviewer said they expected him to give male viera.

All these things start to add that the obvious thing of implementing male viera may not happen.