It was waterfall, but a lot of agile inside. Instead of development from waterfall, developers get a proof of concept up in front of the client SMEs as soon as possible, and then get it into their hands testing as soon as possible. In this way, the people working on the requirements were intimately familiar with the inner workings and offering feedback very quickly, to save time if solutions weren't working as intended. Each team would have 3-5 major projects so as soon as the first project didn't fill the full meeting, other priorities started getting their requirements. These meetings would be a touch base and rehash old topics if any solutions needed a pivot.

Once the SMEs and developers signed off on the solution, then it could go to the test part of waterfall, system test, everything launched once during the rollout window. And then maintenance mode.