An airplane will slide nicely on concrete, but may hit a soft, high, or low spot that causes him to slide sideways, hence increased odds of hooking a wingtip & cartwheeling.
If the engine is off prior to landing gear-up, the starter can be used to "bump" the prop to a position where it won't strike the ground on landing. Therefore no damage to engine or prop.
“bump the prop” - great idea.
Has it ever worked?
One prop strike, you buy a new engine, no matter how nice it runs.
Assumes 2-blade prop - can’t be done with three.
Even with the prop out of the picture. The grass can be full of uneven surfaces. I’ll take the concrete,