Ah. The good ol' half truth thrown out as a full truth by an "expert".
Unracking will not wreck your shoulders. Unracking with a soft/loose back might, but shoulder issues come from the bench press movement itself, not the unrack. Flared elbows with a soft back will fuq up yer shoulders.
Having pins too low can cause issues with heavier weights. Normal gym bench presses are shit. Use the squat rack if you have to to get your bar height right. Have a look at the "so you think you can bench" videos. Unrack should be about a 2-4cm movement, not a quarter rep. Its mostly a pull out, not a lift up.
A spotter is there to take part of the weight on unrack so that your back and traps stay tight, not because it might hurt yer delicate shoulders. If it's not tight to start with, then the hand off is pointless.
And ferfuqsake. Deep squatting will not wreck your knees. Not deep squatting will wreck your knees. The patella (kneecap) is surrounded by fibres attached to your quad. Your hammies attach to the upper shin. If you only do half or 3/4 squats or even "just above parallel", otherwise known as capo squats (cough), then your quads are pulling away at your kneecap. After a few years of that, you gonna have issues. When you squat to proper depth (hip crease below the top of the knee) then the quads stop pulling and the glutes/hammies take over, with the hammies pulling your shin into place below the patella.
If you have knee pain, stretch your quads. Pretty much instant relief. I'm not talking about a knee injury or tendon tear, just that annoying kneecap pain.
This first vid looks at the unrack and pin height issue.