git archive is a fine way to produce the release tarball. But it's not guaranteed to always, forever, be able to reproduce the same thing. That makes it unsuitable as a replacement of the tarball itself.

Release artifacts must either be reproducible or they must be treated as precious, irreplaceable.

Further, using a complicated tool to reproduce something seems inherently like a worse idea than to keep the something and not have to rely on a way to re-create it.