Jadnashua
Retired Defense Industry Engineer xxx
The tub doesn't need to be bonded to the floor. You can use some shims on the existing feet to get the slope you want along with some construction adhesive, and then use the piles of mortar for final fine tuning. Do not try to make a flat bed of mortar, as you won't be able to get enough pressure to then level the tub (thus, the piles which will cause more pressure on a smaller area that will collapse as you press the tub down). The tub will feel more solid and last longer if you bed it into piles of mortar. Otherwise, over time, you'll end up with stress cracks, and it can fail. That will likely be outside of the warranty, so the company won't care, but in the meantime, as it cracks (crazing - small cracks), crud will get in those, discoloring things, and eventually, it gives up and fails. Happens faster depending on how heavy the people are that use the tub.
It's your house...use the advice or ignore it.
It's your house...use the advice or ignore it.