I think waterfall and waterfall-ish development is more prevalent in government contracting. You aren't building for yourself, you're building for a single external customer, and you have to build both the functionality and the interfaces that they want.

And I note that government contracting was probably a bigger fraction of all software engineering in the 1980s than it is today. (Still more in the 1960s.)

So, yes, it was real. It is mercifully less prevalent than it was.