I think the low preorder numbers are due to a few things.
1)Japanese fans, and JRPG players in general, are a little more savvy than people who buy up Blizzard or Bethesda slop. After Forspoken and FFXV, people are a little leery about XVI. Square's put out a lotta just dogshit content over the last few years and their reputation has really sunk.
2)The PS5's userbase still isn't where the PS4's was at when FFXV launched. Sure, there are plenty of units to go around now, but the adoption rate still isn't there for whatever reason.
3)Japanese players think the lead looks gayer than Cloud. I've seen sooo many Japanese dudes on twitter and futaba bitching about how faggy he looks. Not as big of an issue as the other two, but it's been making me laugh for a few days now.
I think that if FFXVI is a good game, the numbers will start to trend better over time. It might not do the numbers Square Enix wants right outta the gate, but they have put themselves in a position where they're really going to have to work to lure consumers back.