On a philosophical note, git, being a distributed source control system has no limits to repo sizing, but github, being is a centralized "hub" suffers scaling problems. It's fascinating to watch these tradeoffs play out. Maybe, IPFS would come to the rescue one day.
I don't understand where git's distributed nature comes into play here. Perforce is fully centralized, and it also doesn't have any limits to repo size - as long as you have enough disk, P4 will handle it.
In fact, Git's distributed nature actually makes it infamously bad at scaling with repo size - since it requires every "participant" in a repo to have a copy of the entire repo before they can start any work on it.
This is where something like VFSForGit [0] helps out. Instead of cloning the entire repo, it creates a virtual file system and fetches objects on demand. MSFT uses it internally for the Windows source tree (which now exceeds 300GB).