Oh my, looks like the person who translated this got carried away a bit.
It is true that pies might be a colloquial word for “policeman”, but it is much more disrespectful and outright vulgar than “cop”. People who call the police “psy” are mostly rebelious teenagers and football hooligans (and Polish rap artists).
We have a word whose connotations are much closer to “cop”: glina, or sometimes gliniarz. Though it’s a derogative slang word, it’s not half as vulgar as “pies”. You can often hear it in daytime television shows. “Pies” would be a no-go there.
Literally, the word “glina” means “clay”. I had no idea how this word came to be used to refer to policemen, but I’ve just looked this up and it seems that people in the criminal underworld associated the police with a certain “sticky” quality, as in “likely to find and catch you when you’re up to no good”.