With the right context both are pretty good actually.

I think the emoji one is most pronounced in bullet point lists. AI loves to add an emoji to bullet points. I guess they got it from lists in hip GitHub projects.

The other one is not as strong but if the "not X but Y" is somewhat nonsensical or unnecessary this is very strong indicator it's AI.

Similarly: "The indication for machine-generated text isn't symbolic. It's structural." I always liked this writing device, but I've seen people label it artificial.

Em-dashes are completely innocent. “Not X but Y” is some lame rhetorical device, I’m glad it is catching strays.

When I see emojis in code, especially log statements, it is 100% giveaway AI was involved. Worse, it is an indicator the developer was lazy and didn't even try to clean up the most basic slop.