Vendoring means you don't have to fetch the internet for every build, that you can work offline, that you're not at the mercy of the oh-so-close-99.999 availability, that it will keep on working in 10 years, and probably other advantages.
If your tooling can pull a dependency from the internet, it could certainly check if more recent version from a vendored one is available.
If your tooling can pull a dependency from the internet, it could certainly check if more recent version from a vendored one is available.