Thanks for posting that, Ryuman.
@cold_spirit
The short version in case you don't want to read the full article: An E3 pamphlet from 2004 in anticipation for Advent Children referred to the planet's/world's name as Gaia. Fans assumed this was the new canon name for the FFVII world and from then on the name would pop up in English marketing materials up to this day. The name however has never appeared in any of the FFVII titles proper and never been referenced in any Japanese sources, so it is purely a mistake perpetuated in English media.
For some people the prevalence of the name in English marketing material is enough for the name to be canon. I've even seen arguments that by virtue of how long the mistake has been around it has supposedly BECOME the correct name by now. I disagree with these assessments.
Recent example: Launch trailer for FFVII on Nintendo Switch and Xbox One, as posted on the official English Final Fantasy YouTube channel.
In other words while I disagree with the notion that the collective consciousness of "enough people" has MADE the name official, the fact is that this error isn't going away anytime soon if at all. Too many sources have used the name and will continue to use it. All because of one goddamn pamphlet from 2004 that made FF7 message boards go "Oh well, I guess this is a thing now".