If you land on something and slap like a curb, you could break an arm. And you could land in lava.
When you get good enough to not need to slap, then you have good ukemi. I mean not slapping after hard throws.
I don't slap 99% of time because I don't need to. My body knows how to fall and what angles so I don't have to slap and can work on my ground escape that second faster.