This account doesn't have the "Exactly 123456 Player Points" achievement in the awards section. Shouldn't I have it if I have the "50 Million Player Points" (which I do have)?

~bumping~

I think you're meant to get it when you have 123456 player points at that time, it's quite random/hard to get :(

But I should have it because I have the one for 50 mil player points and that's more than 123,456

You don't always get it, you more than likely skipped past the 123456 stage, unfortunately its very rare to get because of how the point system works, it doesn't go up by 1 point all the time