As per the previous request for classic for syft, grype also fits the same requirement for classic confinement. As @popey was previously vetted in Request classic confinement for syft - #8 by 0xnishit as a trusted contributor to the upstream syft repository via his popey (Alan Pope) · GitHub account, and I can see he is also a contributor via this same account to grype - Commits · anchore/grype · GitHub - we can conclude he is also a trusted member of the grype upstream (not to mention he is employed by the maintainer of grype, Anchore).
As such, the requirements for classic confinement are understood and I have vetted the publisher. This is now live.