Romanian deadlifts are done off the floor. Partial deadlifts are done off pins.
For gluts/hams, you should try straight-leg deadlifts. Done off the floor, knees straight or nearly straight, and focus on pulling up the weight with the hams (keep back straight). Regular/Romanian deadlifts also...
I do them up against a concrete wall in the garage with a couple of car stands on either side and it doesn't go anywhere. A corner would be even better but I can't reach any of them.
Great exercise.
How heavy do you go on the flies and how bent are your elbows? Do you let the weight go down as far as possible to get a good stretch? I haven't done flies in years.
By the way, these threads are a great idea. I really liked the shoulder one.
For everyone, I don't know.
For myself, I'd have to say myth. Because I really screwed up my back one time doing front squats, and have never hurt it doing atf back squats. Although my back is fairly easy to screw up.