This website says it is no longer maintained, maybe a more fitting link to the NIHR Centre for Engagement and Dissemination could be added instead?

It is debatable if negative results can be published easily. Of course they should, but recent studies have shown that it's often not achievable to get them published in peer-reviewed journals even if researchers are willing to. (For example here). Maybe I have just misunderstood the context of this sentence? Of course reproducibility makes it easier to publish both positive and negative results in general. But the linked article relates to making them publishable in reputed journals and that is still difficult in many fields.