Personally, I don't feel that soaking in water is an "alteration" because nothing unnatural or unoriginal is being added to the card or removed from the card in any way. Only superficial dirt and stains are lifted away from the card and there are no chemical or physical alterations to the card stock. "Power erasing" may be slightly different as this may remove a light layer of the card fibers along with the pencil/ink mark so, in a sense, this does alter the original composition of the card. I think everybody would agree that the other things you mentioned (pressing to widen borders, trimming, etc) are alterations for that exact reason.
There will probably never be universal acceptance of soaking as there are some who feel that absolutely anything that changes any aspect of a card as it is originally found is an alteration. In my opinion, if one subscribes to that viewpoint, they must view the card as already having been altered when the dirt/pencil/whatever was added and, in fact, any card that is not gem mint directly off the press would in some way be altered.
To answer the original question, by the way, E93s and E95s both soak very nicely
