Oh yeah, support staff aren't always aware of everything. For example, with one of our latest features, we didn’t have time to add a UI option to disable the feature. The expectation was that support staff could disable it via their special admin panel upon user request. However, I accidentally discovered that when users asked to hide the feature, tech support told them it wasn’t possible! It turned out the tech support lead forgot to share that information with the team.

As for the OP, they should have conducted load testing and implemented rate limits on their end, rather than blindly relying on someone’s word that GitHub was ready to handle all their product's load for free.