There are a lot of concerns and a lot of assumptions, but not enough testing has been done to condemn these BBs yet.
The point was made that regular BBs don't deform much under normal shooting conditions and I'd have to agree with that point. I used to shoot a 400FPS gun with a 6.03 Prometheus tightbore at my basement targets (mainly cardboard) and reuse the BBs (KSC Perfect .20g). I would gather the BBs up after I was done, wash them off, pick out the shattered ones, then re-oil them and load them back up in the gun. Never had any jams.
RS Type 56-1 & RS Type 97B & KWA M11A1 w/steel kit
KJ M1911A1 & KSC G19 + AI Grenade