...huh. I would have expected to pin to a commit (by hash), but that shortener link has nothing like enough address space to be doing that, so yeah that's a poor arrangement. But you could point to a commit, which I would think is quite good.
To be fair, it is an immutable shortened url, but it could still point to a random site that then redirects to a git url (when it's being benevolent). Definitely better to point directly to a git commit hash, though still a bit sketchy regardless.