Documentation has a cost, and a risk. It must be maintained when the code changes, if not one deceives future developers and increase the chance of bugs. Ideally the code itself should be documentation enough; keep code comments for complex parts of the code which are not obvious -- these comments then stand-out because they are rare.
The only place where you should document the obvious is in the public API, so I'd say the existing team are probably on the right path. Sorry :-)