Unless they have a qualifying time for NB bodies with penises which is different from the one for NB bodies with vaginas? That would work.
Wouldn't it only work if they were natal penis/vagina rather than artificially constructed as part of a transition followed by a realisation of NB status, IYSWIM?
In fact, picking my way through the various non-definitions of man/woman/NB and guidance on how to discuss such sensitive matters, I'm not sure that I can explain what I mean. 