It certainly hasn't been well-publicized as to how it works in practice, especially for a large brand. Do they opt-in or opt-out the sellers? Do they have to choose just one of those two models?

For large brands, this brings up yet another antitrust concern. If they suppress the grey market (or even create too much friction for their authorized resellers), big brand manufacturers run the risk of running afoul of even the modern, more lenient antitrust law interpretation by pushing up consumer prices.