>>37013076>>37013110Wait, there's an actual debate about this? Why isn't the answer obvious?
If it's available in the main Gen 7 games (SM/USM), it's Gen 7. If it's not available in a main series game until Gen 8, it's a Gen 8 Pokemon. The fact that it's available in a non-main series game is irrelevant, as Pokemon have been available in side games earlier than their main series debut before, without affecting which generation they're considered part of.