Like many many people
Someone may correct me, but i don't think the phases mean that much any more.. it was more a ''we will do it in this order'' kind of thing.
From users comments on the forum, it appears that while those phases are being implemented, so are many of the other phases.
Although people look on the openreach website and see that ''fibre due by march''.. ofc, all that means is when openreach are going to upgrade the exchange. They still have the much larger job of pulling all the fibre to all of the cabs in the area.
Which can take months and months.