Yes, it seems like the CZ-806 BREN 2 and CZ-807 (7.62x39) are in fact different sub-families of the CZ-805 BREN. But from what I remember, the CZ-807 predates the CZ-806, it came around the time of the CZ-805A2 in 2013 and was made for India's rifle trials. So it doesn't benefit from the CZ-806's improvements in recoil and weight.
What could end up happening now is that we see another sub-family, one that aims to tackle 5.56 NATO, 7.62x39, and 7.62 NATO while also building on the improvements of the BREN 2. Maybe a BREN 3?
CZ 805 weighs 3.60 Kg, CZ-807 weighs 3.31 Kg (x39) while CZ 806 Bren 2 is around 3.10 Kg.
The CZ 807 trialed by India failed (or some officials made it fail due to no offer of kickbacks ). The CZ-807 trialed by PA passed to become one of the three finalists. I assume they offered an improved version to PA. It will not take them much time to come with a 7.62x51mm version of CZ 807. Otherwise, they can offer the x51 BREN 2 variant.