Pretty sure SE repeatedly advertised, over a month in advance, of the day one would have to subscribe by in order to get 3 full months of subscription in before it's too late.

I got like 3-4 emails regarding this matter alone. Personally, I was eligible and got my status as soon as the campaign was announced, but this email blast was part of their newsletter - same email series that let people know about chocobos and shit.

So, the statements that SE didn't give a heads up until it was too late is bogus. It wasn't only emailed multiple times with an explicit date by which one had to subscribe to ensure Legacy, but it was included on the Lodestone, too.