Er, old news?
This kind of thing has been standard across central government since FoI became law 10 years ago. You have to choose to save off the important stuff (and there are archive systems to do this) and then everything else is cleared after a specified period of time - No10 have 3 months but I think the rest of Gov have between 6 and 12 months as the limit. Remember,this stuff has been in place since 2005 - storage was really very expensive back then and Gov IT budgets are limited (remember they are funded by taking money away from you as taxes).
The FoI Act specifcially did not include a clause to stop people deleting stuff before a request has been received to allow removing anything unimportant / incriminating (delete as appropriate :) )
Of course, deleting stuff after receiving a request will get you in a load of trouble.