How? Because currently the OIA allows a request for official information to be refused if "the information requested is or will soon be publicly available" [emphasis added]. At the time of its enactment in the early 1980's this was justified on the basis of similar laws, notably Canada's Access to Information Act, and the first part seems completely justifiable. As for the second, the Danks Committee justified it as "a protection against requests for the content of a speech not yet delivered or a press release not yet made". Which seems reasonable, when the speech is being given tomorrow or even next week and in an environment where there is very limited proactive release. But it works very badly where proactive release is common.
How? Here's an example: last year Climate Change Minister James Shaw gave me one of the most egregious "fuck you" responses to an OIA request I have ever seen, withholding both documents and their titles on the basis that both would "soon" be publicly released. The underlying justification for this refusal was the government's proactive release policy: climate change advice is usually proactively released on MfE's website. The problem, is that that release is neither timely not certain; release requires explicit Ministerial approval, which seems to take months, and some documents don't show up at all or take years. In this case, they did eventually show up after a few months - by which time they were less topical and useful to public debate.
And that is the core issue: the point of freedom of information law is to give the public information when we want to know it, not when the government decides we should know it. Absent amendments to section 18(d), or a clearer message from the Ombudsman that they will enforce their current advice that it should not undermine the purposes of the Act, what this change is likely to result in is a complete reversal of that principle, and a return the the pre-OIA practice of the government doling out what it wants us to know, when it wants us to know it. That would be substantially worse than the status quo. And if that's going to be the case, we should reject this "reform" and tell the government to give us real, requester-driven transparency instead.