The rumor is rooted possibly in the lines of plumbing/electric/other fixtures that are sold at big-box stores (Home Depot, Lowes, etc) versus being sold at dedicated trade supply houses. There are sometimes special runs of fixtures with particular low-cost high-volume features that box-stores sell that may be inferior to the trade house equivalent.
A lot of these items are off shore. The quality is lower than what you will get from a dedicated supplier. I see this a lot in the trade.
Not so with guns.