To begin with,
It seems first BB pots were manufactured in Western Iberia. But the spreading of this pottery style has been so quick...
Nothing proves us first BBers were of Y-R1b-P312 stock. If no error, their Y-haplo's were variated, maybe of Neolithic origin or Megalithic, spite not by force local.
It seems the first BB users and makers lived outside the first Chalcolithic fortresses. Their pottery untruded into the fortresses a bit later, not in complete set of forms but only under selected forms (fine, often 'maritime') rather than domestic forms. Nothing tell us this kind of selected pottery entered the fortresses with numerous people, and a fortiori, brought by conquerent people. To me it seems the pottery was adopted by Chalco people of some kind (Y-R1b-P312?) in Iberia. The propagation into other parts of Europe where R1b dominated too could have been realised through a common network between these elites, or maybe by a distinct group of prospectors having created this network, R1b or not. In fact, BB's settlements in western Europe has been rather spotty first.
The BB area, so huge, was surely not so homogenous that the published maps suggest (often the cas of historical cultural maps). The pottery does not tell us everything about population ethnic and genetic homogeneity.
I stop here for now, because I'm still a bit puzzled by this phenomenon.