Oh, I have a very clear-cut definition for it: if BT has their own CPE firmware development team (ie. uses their own programmers), then they are CPE developers. It doesn't matter who builds the hardware.
The worst of both worlds though would be to force 3rd party manufacturers into creating bespoke CPEs through contract, hence preventing the manufacturer from using the same firmware worldwide with only small changes of factory-preset configuration to cope with national line requirements. That would be the route to higher cost and lower reliability.
Bespoke branding is something that only the peculiar worldview of management finds necessary.