It's pretty soft, but the cannelure and locking ring help keep the jacket and core together. The NBT has a thicker jacket near the base, but nothing to keep it from separating.
Having that extra 23% mass sure doesn't hurt either. 65% weight retention on a 100grn pill is a lot less than the same retention on a 123grn when you need an exit wound to drive a blood trail.
It's rare for me to recommend an SST over an NBT, but deer hunting in the Grendel with a 123 instead of a 100 is one case where I'd make an exception.