That's BS... Not true.
All of the polymer guns actually need less care than their metal counterparts - Not to say you should abuse them - but, just keep the rails on the frame oiled, and also oil where the muzzle of the barrel goes through the slide, and where the barrel block rubs on the slide.
It sounds like he is one of these Glock fanatics who hate ANYTHING but a Glock (go to the Glocktalk website, and you will find them there). Is a Glock a good gun? - Yes. Some people like them, some don't. But, HK was making polymer guns before Glock even came out.
You would physically care for a Glock and an HK the exact same way. Many people have their own quirks about what oil to use/how much/where to put the oil, etc. But, the guy is either lying, or he is ignorant of the facts. He's probably just repeating something that another "expert" told him