I noticed this as well. No matter how dedicated the team is to not doing waterfall, waterfall nearly always creeps its way back when anything that even smells like a deadline rears its head.
Waterfall planning tends to get ramped up for four really common reasons:
* Managers who simply cannot conceieve of non waterfall planning.
* As a response to failure (ironic coz it tends to increase failure rate)
* Because it's basically the job of most middle management to do waterfall planning.
* Because if your managers manager wants deadlines, tough shit it's deadlines all the way down.
* Because ultimately, upper mamagement tends to prioritize control over profit even if that control is somewhat illusory.
Waterfall planning is kind of infectious, too - if the team does it in one area it spreads to others.
I would say that 90% of teams experience this kind of "waterfall whiplash".
I worked on a couple of teams where upper management didnt set deadlines or create roadmaps or anything. These rare occasions were the only time when I was entitely free of waterfall and we were way way more productive because of it. Like night and day.
However, 90% of companies can't even envision this, let alone do it. Most people dont even believe its possible - developers included.
I suspect this is one component of the secret sauce of high performing startups that defeat wealthier, more established incumbents.