Do big-box stores sell inferior versions of plumbing fixtures?
I phoned Kohler to ask them this exact question. The answer, at least for Kohler, is that if the part number is exactly the same, the product is exactly the same. However, some parts, sold only at the Home Depot and Lowe's, have an "R" prefix on the part number. This stands for "retail" and can signify that cheaper parts have been used to reduce cost; for example some metal parts may have been replaced with plastic parts.