Leaks, like live-service games and always-online requirements in single player titles, are one of those realities of the video game industry that we've just got to live with.
Leaks are a bit different from the other two though, in the sense that they've been around much longer, and are usually perpetuated by the community, not the companies (except when bug leak things first). They also very often get debunked, but not often at warp speed like this latest GTA 6 rumor.
Grand Theft Auto 6 is one of those nebulous projects were we know it's under development but it hasn't been announced and isn't being talked about by the developers or the publisher despite having passively osmosed more hype than some of the most heavily marketed AAA games. It's been said that Rockstar Games could tweet the image of a palm tree and break the internet harder than celebrity posteriors.
With the main rumor on the block being that the next title in the franchise is taking us back to the pseudo-Miami of Vice City, every minor detail that can be made to fit this narrative is being latched onto both by fans and by rumor mills looking for clicks. This is what happened just recently, when a leaker erroneously drummed up a 2002 domain registration as the confirmation fans have been waiting for.
Big game companies often don't just secure the specific domains they choose to host their sites on, but a broad array of other domain names that are similar or close, as well as various misspellings and then get all of these to redirect to the actual site. This is done to idiot-proof the system and also prevent "domain jockeys" from snatching a similar domain and either profiting off it or extorting the company. Look no further than the famous lawsuit between Microsoft and MikeRoweSoft.