Yes, what a fundamentally appalling concept, to design Phase 1 in isolation, and then Phase 2 as an add-on. Any transport planner with any competence would design a new route with some consideration of an end product, and build it in stages for practical reasons, they would never propose and build something small and then add to it depending on what's already there, unless there was never any intention to take it further. But with HS2, it's inconceivable that anyone proposing a new railway from London to Birmingham, really didn't think that it might one day be developed further north.
Which means it should surely have been designed as a UK project, at very least in principle. So assuming some degree of competence, and at risk of repeating myself, there is no way that it could have been designed purely as a London to Birmingham project without any consideration of cities further north. And yet in practice that's what happened, which is quite bizarre.