It's a fair question but I had a bit of a chuckle at the idea having a shit ton of emojis in your GitHub readme was the first flag it might be AI. Mostly because I always assumed the opposite - that GitHub readmes were a big part of the emoji ridden listicle training data (the other being slop "news" site/social media listicles) for AIs in the first place. After all, they are decently well written and come with grabbing the code to train from anyways.

Before the rise of AI, I had not seen much GitHub content with emojis at all, much less overused; I suspect their source is actually the latter of what you noted. Either way, it's a negative signal.