Cable risers are a waste unless your floors are a wood subfloor with carpet. I engineered hardwood over a concrete slab,Mine is cheaper !
The Dielectric Constant of air = 1. Wood can vary from just over 1 to 4, depending on grain direction and (greatly) on moisture content.
I seriously doubt that engineered hardwood contains/retains any moisture, hence: no more change than lifting a cable into the air.
Most carpeting consists of materials with horrible Constants.
When your cable's lying on a material with a high Dielectric Constant; that's being added to that of the cable's insulation, changing the 'C' in the RLC, over whatever length.
https://www.electrical4u.com/rlc-circuit/
Dielectric Constant - an overview | ScienceDirect Topics
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