You can't "lock" something that doesn't exist.

[Alucard135]

I'm going to take a crack at why gender lock can be used with regards to Viera/Hrothgar.
there are two ways you can be locked from something
1.You can be locked out, it exists you aren't allowed to access anything else
2.You can be locked in, there is only this option there is nothing else

The latter would allow the usage of gender lock in the following sentence
I have to play as a female if i want to play Viera i wish this wasn't the case i wish Viera wasn't gender locked
asking for the lock to be removed in the above case would be asking for another gender option for Viera something that currently doesn't exist

In that second case, you are correct in saying that. You are technically locked into the female Viera option. But, it doesn't necessarily require only one option to be considered locked-in in that case. Some can extend that into being locked into 2 options. So in that sense, all races are locked into either 1 or 2 genders. So some can easily say all races are gender-locked into 2 options and that they want them all to be non binary.

But the main issue if you were to go with the second case, is that's not the commonly known meaning for the word. So you'll have to explain it every time you use it.