I'm a PC gamer. I have 221 games on Steam to date. I use Steam everyday. I have a high knowledge of computers (it's my job) and I'm pretty much OCD about the stuff that gets on mine.
I don't know what misinformation you read but Steam does not install things without your consent, it does not scan your computer without your knowledge.
The only time Steam could scan your computer is IF you choose to participate to their hardware and software survey. You have all the liberty to refuse.