Mushrooms naturally contain a lot of water, up to 90% by weight according to some sources. This makes them difficult to sauté properly because they will give off that water and end up stewing, at least until the water cooks off. But, they won’t absorb more water if you wash them, or at most a tiny bit. Of course, some water may adhere to the gills, but that can be shaken or dabbed off.
Washing is not advised for a few mushrooms whose physical structure makes it impossible to get rid of all the water–morels and lion’s mane, for example.
Do you think water somewhat washes off mushroom smell? I’ve noticed that some sponge mushrooms: morels, chantrelles after washing and drying loose their incredible smell.