This is the first I've heard of lead bullets loaded reversed damaging a forcing cone.
Obviously, since cones don't have a problem with wad cutters and will last about forever when shot with them, the idea that a reversed bullet will damage the barrel is false.
What damages forcing cones is primarily shooting the hot loaded lighter jacketed bullets, or heavy overloads of even heavy jacketed bullets.
Unless you're using gas checks, it's almost impossible to push a lead bullet fast enough to damage the cone.
It's possible the idea of reversed lead bullets cracking the cone comes from people allowing the lead bullets to foul the cone, then they start shooting hot jacketed bullets.
Most of the S&W Model 19 revolvers that showed up with cracked forcing cones were not cleaned and had cones heavily fouled with carbon and bullet metal.