No. Banks in the EU are subject to regulation, this isn't the wild west. There is no way a Polish bank would demand anyone 17x the net average wage to approve a loan for flat in Krakow. Unless you have a criminal record in which case they could flat out refuse you a loan. You get that kind of demands from a loan shark, not a EU based bank.
It's not unrealistic - Polish banks are under a hell of a lot of supervision when it comes to lending (hence why Poland has little to no exposure to Greece/etc) - and such a ridiculous offer might be made to ensure that they get their money. I have a friend who works as a mortgage broker, and he told me that it's quite common practice for banks to make ridiculous offers rather than to simply refuse - one such example was asking for a margin of 10% on a 2m PLN mortgage.
It's worth pointing out that the law has recently changed to all but ban lending in foreign currencies unless the income is also in the foreign currency. Perhaps they were asking for such a ridiculous offer to discourage him?