Agreed. The constructive adhesive is only for securing the tub itself
to the (soon to be) Durock floor.

That's usually not necessary. Once it's all plumbed and tiled in, it's
not going anywhere. If it's an acylic tub are you planning on using
something under the floor of the tub to help take the weight?

No, I hadn't planned on it. The previous tub was cast iron and much
much heavier and there was never an issue so I think the acyrlic should
be okay. The construction adhesive is mentioned in the tub install
specs as an alternative to a cement bed. It's not much trouble and I
figure it can't hurt, although it won't be as much fun taking the tub
out again should there ever be a need to do so.