Woah, the first time I opened this, a lot of pics were broken, but now they all loaded properly! Did you find the secret edit button?
You're comparing PID to too many things. To me, PID was something unique. Back in 1995 or whenever it was that I played around in one of the demos, the only other things I knew of to compare it to was Marathon, and an ancient black & white mac game called Scarab of Ra. Actually, it feels a lot like a natural sequel to scarab of ra, even though they're completely unrelated (first-person pyramid dungeon crawling about treasure collection, resource management, getting lost and barely surviving).
About those chains... the instruction manual makes a big deal out of the chains being a gameplay element and you should be cautious of pulling some of them, not knowing what they'll do, but these are the only two chains in the game. What a way to underuse a gimmick. It's like removing all the buttons in doom after map e1m1, but PID more than makes up for that with replacing the monotony of switch based puzzles with a wide variety of insane tricks and traps (mostly designed to sucker punch you until you find the right clue or item).