Blu-ray audio confusion

It is not clear whether modern audio receivers that are certified
for blu-ray can handle both the standard dvd 6.1 (channel behind the
listener), and 7.1 (2 channels part way between front
and back speakers).

---

Some receivers are labelled as
both.
Should we assume that we can attach cable for
both systems, or must we cable for one exclusively?
A few blu-ray disks actually for hd audio use a lossy
stream with Dolby ex (6.1)

We need guidance