"former dropbox engineers" doesn't mean a whole lot -- it's a large company where tens of thousands of people have worked over the years. It's not like this is by the founders or anything.
Yea, "former [COMPANY] employee" could mean anything. I'm not sure it's really much of a flex. I'm a former Apple employee. Nobody gives a shit, and nobody should--That doesn't count for anything if I were to do a software startup. It wouldn't even bear mentioning in a press release.