I guess likely they wouldn't have a problem in practice as the harm/cost to GitHub seems negligible in terms of $.
It may look like a good idea to make $ from the other company pricing decisions, but it ignores the very previsible dynamic effects: I've heard about how other companies "unlimited" offers were turned into a different product by some "creative" hackers - only with the previsible effect of said storage/bandwith/whatever then no longer being unlimited.
You could argue that if something unlimited has to "become" limited, it wasn't really unlimited in the first place, but then I'd argue it's a question of ethics and social behavior: being responsible and not overusing resources, even if they are available to you in "unlimited" amounts, because nothing is unlimited in the physical reality we live in.
[1] https://scribe.rip/https:/medium.com/@01010111/managing-your...