Landscape Fabric Under Tub?

On the verge of installing a Swanstone Veritek tub (yes, I know it's not cast iron, but it's the only one that fits my alcove). I installed a similar Sterling Vikrell shower base several months ago and it came with a sheet of spun landscape fabric as insurance against squeaking, which I put on-top of a sheet of thin plastic which was on-top of the mortar base.

The Swanstone unit didn't come with any landscape fabric, nor is there any mention as far as I could see in any discussions of installing tubs on this forum -- only the importance of installing in a mortar base. Should I bother putting the fabric in? Seems like the mortar would conform better without it.

I just put in a Sterling Vikrell tub, tossed the fabric and did the mortar base with thin plastic over it.

All seems pretty good to me, and yes, I think all of the ridges might conform a little better to the mortar without the fabric.