The "full stretch" argument is related to the "working harder" one when it comes to full ROM and strict. Neither holds water in my opinion, been there done that. There's no basis that i can see for the claim that full ROM is any advantage, and it's not safer.
I don't get any shoulder in preachers from doing partials, it's completely on the bis. What you're talking about, rocking at the top is common and is a little bit of cheating on preachers that is effective, can be done with full or partial ROM.
If i do full ROM preachers it highly stresses the area around the top of the forearms/bottom of bis, which isn't what i want to hit anyway. I've strained that area by trying to stick with full ROM to the bottom, and by doing strict. Partials center the effect in the middle/belly of the muscle and are easier on the muscles, besides which if you believe in time under tension/constant tension on the muscle, full ROM isn't as good.
Same thing for squats, my best results were from box squats, not doing full ROM. Not just safer, more effective also.
I just hurt one of my lats from doing full ROM hammer pulldowns. When it's better i'll stay with 80% ROM that weren't causing problems.
If the elbow problem from doing curls was on the inside of the elbow, it's called golfer's elbow. It usually happens from either curls or lat work with certain grips-essentially without realizing it while using those pulling muscles you're also squeezing your elbows and arms together during the exercise, even though it's not obvious. Over time that creates the pain. If you try slight variations and change the form a little you can find something that will work and the pain will go away.
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