Let's say you're working for the DMV on a program for driver's licenses. The idea is to use one structure for driver's license data, as opposed to using one structure for new driver's licenses, a different one for renewals, and yet a third for expired ones, and a fourth one for name changes.

It is not saying that you should use byte arrays for driver's license records, so that you can use the same data structure for driver's license data and missile tracks. Generalize within your program, not across all possible programs running on all computers.