Drop-in tub in alcove without frame or stringers?

I purchased a Kohler Underscore acrylic drop in tub (60"x32") with the understanding that it could be installed in a 3 wall alcove using a tile-in bead kit (verified by Kohler). After the installer looked at the tub, he determined that would not work -- the 2x4 drop-in frame would prevent the tub from sitting flush against any studs because the lip wasn't wide enough to reach. He told me I'd have to return it and buy an alcove tub with apron.

When I called Kohler to confirm, they said the drop in tub CAN be placed against the studs with no frame, no stringers, and no nail-in flange because it has feet. They say just build a frame across the apron and it's fine. But even if I use a mortar base, I'm incredibly skeptical how this tub could not be secured to the studs in any way? I live in prime earthquake territory and this is a 2nd floor condo for what it's worth.

I prefer the drop in style because I can tile the front of the tub -- but I'm ready to bite the bullet and exchange for an apron front with integral flange if I have no choice.

I appreciate any advice before I make any more costly mistakes on this project...
P.S. -- thank you, this forum is a life-saver!

 

Even when a drop-in tub is literally dropped in, most of them aren't designed to 'hang' by the rim, they need a slight gap there that is filled with silicon. As a result, they are entirely supported by their feet or the bottom of the tub. So, if you get the tub sitting flat, and you do want the rim level, too so mortar may be required, once the tile is up, the thing shouldn't move around. The tile flange must be attached properly, or you'll get moisture behind and in the walls and floor.