Earlier quoted context omitted.
As I understand it, it's not allowed for a third-country institution to lead part of an EU project. They can collaborate on specific tasks. The UK joining now means a group at Manchester University can lead the work on health outcomes, not just be a part of it under someone else.
Thank you very much for this explanation, I was confused by TFA (I skimmed through it, its my fault). Like I thought then, it's not a brexit thing at all.
Britain lost that opportunity for several years, which will have caused people and groups to move to the EU.