I think it's because Britain in particular is desperate to get outside support for the programme whereas the Swedes and Japanese want to get access to technolog

I think it's because Britain in particular is desperate to get outside support for the programme whereas the Swedes and Japanese want to get access to technology but design their own aircraft. So the only way to get them onboard is to make the association loose. I can't tell if this is good or bad - it might mean that the Swedes will make something affordable out of it and the rest will blow billions on various Golden Geese (is that the right term?). There's some interesting Japanese technology - e.g. their AESA missile radars would go into the Meteor to bring it far out ahead of anything else. Also I think they have some ceramics in their fighter engines etc which are of high interest.