The fact that it wasn’t dangerous is why it was a penalty only, and no red/yellow card.
It’s an illegal act, and the degree of danger is often determined by chance (does the player land on the other’s leg, is the foot trapped, etc).
"I know you're not allowed to croc roll but that's not dangerous play." 🏴🐊
Dan Biggar and Maggie Alphonsi disagree with Matt Carley's decision to award Scotland a penalty