In Switzerland it's very common that if a hedge fund / financial company wants to hire a specific person from abroad(so he would need a permit) then they post a job ad that basically uniquely identifies that person's skillset, post it on glassdoor or jobs.ch or other, and then either get no response or filter people who think this is an actual opening.
They then go to the immigration authority and say "Look, we cannot fill this position on the local market, we need to look abroad" and then miraculously just the right candidate shows up.
Not sure how frequent it is in other countries, but if you see a ridiculous/incoherent job ad from a smaller company, it might be for a job that's already filled.