Nothing shady about it in my opinion. You're a consumer using a method to make purchases of a specific item. The company isn't a collector being slighted out of anything, they are a big box company getting sales based off the availability of a product. When a company has a guarantee that employees won't hold back product (which I don't care that they do) then we can talk about morality.
I don't know where this product holding fits into anything I'm talking about but on that, I've been told by several GS employees at two of the stores I shop at here that there are policies about nothing is to be held for employees and that it's something they've been trying to stop and haven't been successful in doing so yet. So your guarantee is there, it's just like anything else, some people are willing to do things they're not supposed to. I've also been told that in several FB groups that GS managers are in they have said that they won't accept bulk returns on pops that were bought in large quantities just for the Chases and I think that's smart. Me and my wife are also retail managers and we actually refuse large returns from known resellers. It causes series inventory problems considering what stock we get is based on what we sell, and no doubt GS is the same. Regardless of how you count when they're bought, it causes a surplus because you order x amount and now on top of that you have returns that overfill you and go on clearance losing the store money, or you order less knowing the returns are coming soon which lowers the other pieces you have coming in that may be more desired.
That's a long-winded response and I could go on but honestly it doesn't matter. You're not wrong and neither am I. Regardless of wether or not I agree, I understand your point and respect your opinion.