See H2OBUG's post. A cylinder that free spins means it can spin in both directions. The factory pawl allows righthand rotation only. A free spin pawl retracts to allow right/left spins.
The reason, as stated by H2OBUG, is if a bullet jumps it's crimp then this cartridge "grows" too long and can jam against the barrel throat. One can easily free spin the cylinder the other way and take the offending cartridge out.
Otherwise you're shoving a knife in the cylinder gap trying to force the bullet back in.