I think several of the posters are talking about different units. First, most people who never used their washer/dryer, own one of the Splendide type, all in one models. I had room for one in my last coach, but had no interest in it. Some use them and like them. With this type model, it has a small drum and probably would do okay while underway. I've never owned one, so I don't know if the drum is in a "fixed" position where it doesn't move around, other than in a circle, but my guess is that it doesn't move around like a home unit when out of balance.
A two piece wash/dryer uses a washer with a tub that moves other than in a circle, again, it moves about like a home unit when out of balance. This movement is really not good for the washer while the coach is going down the road moving in other directions.
When you're discussing the Bosch units in the two Prevost coaches, you're talking about a whole different ball game when it comes to installation and quality.
So.....I wouldn't use the washing machine, that is a separate unit, when driving down the road. The dryer would probably be okay, but you're still spinning a barrel one way and bouncing it another way. Will it work...yes....is it a good idea, probably not.