You are NOT supporting the tub by its lip, you are integrating the tub with the wall surface. The only way it would be supporting the tub is IF the legs compressed into the floor, and in that case the lack of a ledger board would create a crack betwen the tile and the tub. AND Kohler tubs USED to REQUIRE a ledge board before they started adding feet to the tubs, and they NEVER cracked.
Right and by "integrating" the tub with the wall surface, the moment the tub gets compressed into the floor or the floor sags, you then are supporting the tub with the wall. Also, that "Crack" you are talking about is one that should be filled with silicone. Not exactly a hard crack to fix. However, by supporting the tub by the wall, you create all kinds of possible problems - the tub becoming out of level, the tub not being supported by anything but the face and the wall, and on top of that the tub not being warrantied.
I'm no expert, but I've worked with enough "seasoned veterans" to know that the "I've done it for 30 years this way" argument is one to be ignored unless good reasoning is supplied.
I wouldn't have replied at all had the thread not been focused on humiliating a home owner who is trying to install this himself instead of paying someone else. If you don't want to run a website that respects the people you're trying to help, then what is the point?