These statements will definitely be denied by the manufacturers
They all claim that their products are unique and that the production processes are secret.
But on the other hand; there aren't that many paper mills and different coatings out there.
What plays an important role is how carefully and "scientific" the producers test the products with all the ink and printer combos.
One way to figure it out is to look at the icc profile quality and profile services they provide.
With a spectrophotometer it's easy to test and determine the profiles accuracy.
/Sven