In theory, that should make you more tired not less. If you are standing on a soft surface your legs and feet will be making constant muscular adjustments. Compare spending a day standing on a carpeted exhibition stand compared to a day standing on a tiled exhibition stand (most salesmen will have experienced that one!)
Having had three knee operations. Two on one knee, one on the other ( I also get twice yearly hyalogen sinovial fluid booster injections direct into the fluid sack that contains the meniscus/cartilage on both knees) I can say from my own experience standing on a soft covered floor is better from a less painfull knee point of view than standing constantly on a hard surface. Less shock gets transmitted through to my knees. I also prefer soft soled shoes for the same reason. My office and workshop floor are carpeted. The workshop in particular at all the work points were I stand for long periods has thick carpet as the floor is concrete.
That item you are on about sounds like US BS though? Whats wrong with sourcing closed cell foam here? There are plenty of companies selling similar foam. It may not have the fancy pvc wrapping, but does it need it if you just need cushioning underfoot? It will be miles cheaper too I suspect.
Have you got a company near you that makes foam? The mix a couple of chemicals on a giant plastic bag and let it do it's stuff. The bag is then cut off with an inch or so of very small bubble heavy foam attatched and skipped.
I have used it for workshop mats, knee pads all sorts.