The standard is for software to report its own EOL / EOS status. The website you linked is the opposite direction - it's aggregating that status for a certain set of software.
Aha. Very good point. SW self-reporting requires buy-in, though, which seems like a pretty high barrier.
I am very much hoping the effort succeeds, but I am also mindful of the fact that the site to which I have linked is more successful by virtue of having better coverage.