Pretty sure he's saying it's not much of a contest when you're spending the same amount of money to get a very similar monitor but you get way more AMD GPU than you would NV. If the monitors are indeed significantly cheaper for AMD GPUs, that'd be a huge boost for an AMD adaptive sync solution because the price difference would help offset concerns about getting locked in.
Let's say for point of example that the monitor will last five years or so, and in that time frame it'll see two graphics cards paired with it (the people who run faster upgrades tend to flip their cards, so the economics aren't as clean but I have a feeling they're similar). If there's a ~$100 difference, that's $50 more to spend on each card. You'd have to be deliberately timing things badly to not be able to get better performance from AMD than from a $50 cheaper NV card (and usually vice versa to be fair).
So with a big enough price delta between freesync and G-sync, the worry about lock-in sticking you with worse cards isn't actually a big worry, and that would make AMD a really sound high-end buy for the monitor+GPU+upgrade GPU solution.
(says a guy with a 970)