Julian Cope presents Head Heritage

No, probably not much actual advancement as we might understand it (and slower, certainly). But a change of viewpoint could just as easily change the plan - you only have to look at Bryn Celli Du, where the stone circle/henge was destroyed to build the chambered tomb. Or a local escalation of a status competition ("they buggers at Marlbro have built a roight big mound"). Even an increase in ambition, over successive generations, or a desire to build upon what their forefathers had done. Lots of reasons why the plan might change over time, without negating the completeness of the original scheme.