Not really but it kinda depends on your goals.

For instance Ruby only pulls dependency graph (from API) and it’s like a dozen MBs. That’s because package installation is very standardized and for most packages it’s just “unzip to this directory”.

On the other hand you have Gentoo Portage. Their main repo is like a GB in size and packages contain not only dependencies but also metadata (licenses, homepage URL, etc.), build instructions, patches and additional files like distribution-specific configs, and portage-specific metadata (ebuild and source package hashes). Gentoo uses git for the repo. It used to use rsync but it was still basically the same: the delta is resolved and a partial update is downloaded.

So in general, in my mind, the main aspect is how much your package manager does locally. If it’s mostly dependency resolution (and dep features are simple) you can do with a truncated index fetch (like Ruby). But if the things your pm does are complex you probably want the full repo.

And the size is the deciding factor. I’m sure it won’t be much of an issue to fetch Ruby index from git. But it might be for large checkouts. Though Gentoo switched from rsync because git does a great job at minimizing transfer size and ensuring checkout integrity. Especially with a smart server. Rsync wasn’t particularly fast either.