Every package gets updated, when there is an update for it. Dependencies don’t matter for that.
Only if a package depends on a specific version of another package, is there a difference. When the dependency would get updated to a version that doesn’t satisfy the version requirement. Then an error gets thrown and nothing gets updated.
But the package maintainers for the official repos don’t really let that happen. It’s more of a problem with aur packages.
There was a deletion request for that package, because it is not intended for x86 and mirrors a package in the official repos. It seems like it was deleted. I remember it getting an update not to long ago.
You can still clone the aur repo and get the PKGBUILD from there: https://aur.archlinux.org/glibc-widevine.git But be aware, that it doesn’t get updates anymore.