Same deal. If they don't call hits, follow up grenades are tossed and entry with rifles blazing happens.
But it depends on the hosts. Some will say you have to be hit. For indoor some will say think about it, if you're in a room and a real grenade went off, you'd probably be dead. For outdoors, it's harder as you'll sometimes get a designated range of impact but we all know everyone's ability to judge distance in a game is super accurate!
It's all on the honour system. If in doubt call out and respawn to go shoot your friend who just killed you!