Just IMHO, scootering any reasonable distance without the crotch strap will be uncomfortable.

I have done some scootering using the waist band in the past (in emergency when crotch strap wasn't available) and it wasn't comfortable as it keep riding up toward my chest.

But it will work for someone who has a "built-in keel" to keep the waist strap in place when pulled by the scooter...