"So one of the major chains (and I can guess which one, although...

"So one of the major chains (and I can guess which one, although there's a small chance it's the US I suppose) has come to them and said we want more of the sale price, more margin, or we'll start featuring more of our own brand or an import competitor and put you in the back???"

Not sure of the point you are making here.

If it's that a chain (a large hardware chain, presumably) has said to GAP, "You need to come back to us with better terms or else we are going to stock a competitor's products," what of it?

It's what happens all the time in distribution channels.