I guess that depends. On GitHub it sounds like the victim is a paying customer of Google Workplace, not just some free account. I had similar genuine calls from hotels, credit card companies, an ISP, my electricity provider etc.
So yes, there are some signs that might make you suspicious, but I guess we agree that this was not just a regular everyday scam but a pretty professional, well-prepared and possibly targeted attack.
I guess so but I also don’t really get it.
“Wanna hang [your dick] out [the wall] later?” might be a glory hole reference??