Sterling Ensemble Install

Working on a basement bath addition and planning to install a Sterling Ensemble pan and wall system. I am going to put the pan in mortar as many have suggested to firm it up. The wall system can be installed direct to studs, but I'm wondering if putting it over a substrate (i.e. paperless drywall), left unfinished might provide a more solid feel to the wall system. It seems like many have used the Sterling systems on this forum, so I'm looking for some feedback. Is adding the additional substrate a useful step to improve the feel or am I just wasting my time???

The walls pieces will stand prouf of any substrate, so you gain nothing in terms of rigidity.

I guess I was thinking that with a direct to stud installation, the panel would only be supported at each stud. If I were to cover with drywall, there would be a measure of support for the panel in between the studs as well. I can't tell exactly how the panels are built and I haven't purchased yet. It seems that what you are describing is that anything between the studs wouldn't be in contact with the panel anyway, so it won't matter if I do it or not.