The only reason I'm posting this is because we have had similar things happen in almost every attempt at using sprints. They're just not suited for any sort of formal/business context where you don't have absolute and frankly religious buy-in to the concept.
A sprint is a discrete period of time in which discrete software development tasks happen. A “rolling sprint” is conceptually void. You can’t have a discrete period of time that lasts indefinitely any more than you can have dehydrated water. The “rolling” part and the “sprint” part are mutually exclusive.
I’m not even saying that they weren’t “doing real Agile” – I’m pointing out that what is being described has literally no meaning at all. You can’t be good or bad at it because it’s a meaningless term.
But there’s no such thing as “one big rolling sprint” though. If it’s “one big rolling…” then it can’t be a sprint. It’s like dehydrated water. It’s conceptually incoherent.
To untangle the wording of this, when you say your process became “one big rolling sprint”, what you’re actually saying is that you stopped using sprints, aren’t you?