Don't know about the formalization by Royce, but I've witnessed and suffered waterfall in practice - let's call it ad-hoc waterfall if you will - and it was no urban legend.
And on moonless nights I still wake up screaming remembering a RUP project I was involved in around 2000.
And on moonless nights I still wake up screaming remembering a RUP project I was involved in around 2000.
"No true scotsman" and all, I know.