Dolby Atmos is a mixed system with channel beds in the traditional positions and objects that can be placed. Mapping objects in home-Atmos is to the fixed layouts supported by the PrePro.
Channel beds are essentially channels, the notion that it is completely object based was marketing fluff.
Also, when asked during an interview how many channels were supported on home Atmos, Craig Eggers (of Dolby) stated no channels are lost. For me, that was a hold onto your wallet moment
- Rich