Hate to sound like a strawman, but: why should this my problem? Unfortunately that's the nature of the game. Many software roles are like that. You just have to apply anyway. Other hidden biases women face, OK, got it, but this is a problem that occurs before any dialogue takes place.
Now whether or not that advice gets properly dispensed is another issue.
If you want to hire the best person for the job, why wouldn't you want to do what you can to avoid discouraging good candidates from even applying in the first place?
If they are so timid as to not even rise to the challenge of applying for a job with some uncertainty, how can you expect them to deal with uncertainty in the field?
They assume the job requirements are real expectations. That is not uncertainity, that is taking people by their word.
I would also point out that many good programmers don't like uncertainity (notably those with asperger), it is one of few jobs where it is a good thing. Not implying they are all rock stars, just that un certainty here is red herring.
Because that's a nonsensical strawman; those things aren't even related.
Personally, I see any employer advertising for a position with stricter requirements than what they'll hire as advertising their own dishonesty. It just makes them look bad.
It's mildly dishonest, but it does help you as the employer get closer to the ideal fit for the position. Especially one that is likely posted to a public forum.
The fact that candidates that pre-select themselves out of being chosen is not really a big concern. Why should it be? The way around this is knowing exactly who it is you want for the job, but in that case I wouldn't be posting the job in a public forum. It's kind of what recruiters are intended for.
Now whether or not that advice gets properly dispensed is another issue.