Our's does the same thing. We can level without first dumping and get more travel out of the axles. We have had the airbag pop ddoing it too. Some coaches have greater range.
We carry a number of boards and the orange pads too. Frequently end up using them or some of them under the rear tires instead. It's an aggravating procedure to first level and then determine the number of board, back up and drive on to the center of them. The mfgs say not to raise them off the axles to level.
A great many sites look level until the coach says otherwise, though.
We have done it one or two times but I don't feel comfortable doing it.
The air bags do have enough vacuum power to keep rear axle or the front higher than jacks.
Simple escapes me sometimes. We could have just put boards under tires whil up and lowered and board under front jack.