The short question is this: would a low-flow shower head cause some kind of increase in pressure to the water supply pipes that would cause a rupture and leak?
The longer story is this: I removed a previous stationary shower head and replaced it with this hand-held shower head (http://www.homedepot.com/p/MOEN-Propel-5-Spray-4-5-in-Hand-Shower-in-Chrome-26040/300676251). There was nothing unusual about the installation, it worked fine and there were no visible leaks.
About two weeks of daily use later the hot water to that bathtub faucet and only that bathtub faucet stopped working. A plumber came out and replaced the cartridge inside the handle (http://www.homedepot.com/p/MOEN-Posi-Temp-Pressure-Balanced-Shower-Cartridge-1222/202059049) saying that sometimes the temperature regulator inside the cartridge stops working, just one of those things.
Hot water had returned, we went back to daily use. About 4 days later we heard water behind the wall and found our downstairs bathroom below the shower in question was flooding from the ceiling. We turned off the main water and waited for the plumber to come back out.
He found that the cold water supply line to the shower handle was leaking significantly at a solder point. His initial diagnosis was whoever installed the line had done a bad job soldering the pipe and it had finally given out. He cut out the pipe and replaced it with his own, presumably superior, soldering job.
After he was done, as he was using the shower head to clean out the tub he mentioned how much he hated these kinds of shower heads because they restrict the flow of water so much, and that since "that pressure has to go somewhere" the new shower head was likely the cause of both the cartridge replacement issue and the later leak.
I would agree the shower head does not put out the most impressive pressure, but it doesn't seem anemic or problematic. I can't understand how a restrictive shower head could ruin a scald protector or supply line. Is this actually a thing? Should I look to replace my shower head, or was he just looking for something to be the cause that wasn't him? If not the shower head, could the cartridge be doing something that would cause the pipe to leak?