That would only work if the original was uploaded to GitHub before the copies. Like, somebody could copy from GitLab or BitBucket. And git histories don’t always help if they’re not copied over.
But copyright law doesn't really care about how you prevent infringement, just that it doesn't happen. Isn't it up to Github to come up with a way to do it, or otherwise not do it at all?
GitHub just needs to show they have taken reasonable precautions, and if a conflict is identified, that they remediate it without undue delay.
It’s not a binary all perfectly or nothing at all. The law looks at intent and so doesn’t punish mistakes or errors so long as you aren’t being malicious or reckless or negligent.
> No provider or user of an interactive computer service shall be treated as the publisher or speaker of any information provided by another information content provider
So the act of hosting copyrighted content is not actually a copyright violation for Github. They're not obligated to preemptively determine who the original copyright owner of some piece of code is, as they're not the judge of that in the first place. Even if you complain that someone stole your code, how is Github supposed to know who's lying? Copyright is a legal issue between the copyright holder and the copyright infringer. So the only thing Github is required to do is to respond to DMCA takedown notices.
