I wish more developers would do things like that, seems like a really great opportunity to simultaneously give people a little break from their usual work, let them work on brand new ideas, and build teamwork within the company.
I agree, and at the same time I recognize why most companies don't do it. DF took this approach as a survival tactic; it has thankfully worked out for them. At companies where things are running "smoothly enough," taking the company offline for a couple weeks to do something else is rarely feasible due to the overall multi-project schedule, and the financial bottom line is that there's no readily apparent benefit to the financial hit.
One company I worked at shipped a AAA game, and had another project incubating. The incubating team suddenly was "gifted" with about 50 people from the just-wrapped-up AAA team. No warning, just "hey, deal with a 230% HEADCOUNT increase." Over the next few weeks, those staff were brought back piecemeal to the AAA team before the incubating team was also redistributed to the AAA team or laid off. The "gift" was actually just a financial move to keep the AAA team's running cost down and attributing write-off for a month-plus of 50 people's salaries to a game they'd already decided to kill.
I'm kinda happy to be away from all that, lately.