If they choose to keep secrets to themselves thats fine, I just personally think a little more openess would encourage more people into the hobby thats all. I am in no way against people keeping info to themselves.
What I do have a problem with is if they are infact lying (not saying they are it just seems that way in my opinion.) then thats not fair on people who were hoping to breed and get into the hobby and in the long run gives others in the hobby a bad name and has a detrimental affect on all of us.
If they do have some way of sexing that none of us know, hey good on them, its completely up to them to share or keep for thamselves. Id rather they shared of course. I just happen to think, and it is purely my own speculation, that they are not being honest about being able to sex at 100% certainty so young.