The key difference here is personalization.
Traditionally, if a message was personalized it fell under 'cold outreach' and users were more likely to interact and play along. Just like what happened with the author (the same applies for everyone).
It's like the difference between receiving a flyer vs being contacted by a sales representative. Even if it's they advertise the same product, the perception is different, the results are different.
If you're mean the difference from a pure technical spam detection perspective, I'm not familiar, but would love to read more about the subject and the state of the art techniques if anyone has some resources to recommend.