Amazon employee here, but the statement I'm making is of my own.

Internally we treat customer names and email addresses as the second highest data classification. The highest one is credit card/financial/password data.

What does it mean? It means that there are a bunch of requirements that a software team must fulfill and pass (reviewed by an SDE trained in the process outside the team). This makes accessing this sort of data a PITA for a lot of people, and I can see why they why they would send out notifications when a breach like this happen. Amazon takes security very seriously, and it in fact creates quite a bit of friction to many engineers. However, I'd rather than than the break things and ask for forgiveness model like some other companies (not going to name names here)