For what it's worth,
I have done a few dozen homes with Disposal & GD on a single 20-amp ckt. Never had a call back.
However, I do run a 12/3 MW ckt to a laundry room if the dryer is gas-operated.
I believe that the possibility exists that a load of wet clothes in the dryer and a load of wet clothes on the spin cycle of the washer may trip a single 20-amp ckt if the motors start simultaneously.
Absent any nameplate data, I think it is a safe bet.
