This is not a myth at all and I honestly dont see how a hiring manager can hold the belief it is a myth.
I work with undergraduate and masters students every day as a consultant and as a project manager leading an international team.
Just this morning I personally wrote an hours worth of pair programming with a masters student who struggled to write for the last 8 months.
Just to be clear, I'm experienced and proficient but I work with two people who are both smarter and more efficient than me.
If there is a myth to the 10x programmer, it is that there are 100x programmers.