Yes, coil springs can be dangerous. I recall seeing/hearing one come out violently once when I was working in the Keesler AFB hobby shop (probably someone who didn't know any better). The shop manager (a retired Master Sergeant) got all worked up and in the face of the young airman who was working on it. At that time, the sergeant/manager said to always run a safety device (chain) thru the spring and around the frame - ends of the chain bolted together) to restrain a coil that wanted to leave before you were ready for it..
I've always followed that advice, and only one time was the chain really necessary.. but it's a good precaution...
I moved/re-installed my Z28 springs (removing the originals, installing the replacements) without a compressor. I always run a length of chain thru the spring and thru the A-arm or around the frame when doing either of these task, because what you say is true (they CAN be very dangerous).. but in the case of removing the EY's and installing the replacements (in my case) there was little energy left by the time I'd lowered the lower control arm.. and I was able to get the new ones in place and put a floor jack underneath to install the replacements (although I did have to set my engine/trans back into place in order to get the ball joints reconnected. (the engine was installed when I removed the springs, but not installed when I first began the front end rebuild with the new parts)...
Gary