Bullet tumbling has nothing to do with the targets. How the hell would a bullet know it was heading for a paper plate? They tumble when they cannot stabilize while spinning (or if they hit something hat destabilizes them)Try shooting at paper plates or card board and see if it continues to tumble.
My R700 223 with a 1:12 twist will do that every time with a 75 gr AmaxI don't think Ive ever seen a keyhole that distinct.