Government ministers are bound by collective responsibility and so if Milliband states something definitively it is taken as government policy. All other members of government would be expected to say the same thing.

So the weasel words here are because it’s not agreed government policy that they should leave X. I expect they haven’t discussed it. If he’s more definitive it would potentially expose a split in opinion within the government (Oh the horror!).

Understand the code words. His opinion is that they should leave. This is his way of making it a topic for discussion in the government.