I don't think the two hypotheses are mutually exclusive. A place well suited to a ritual burial (for the reasons of not attracting carion feeders or otherwise n

I don't think the two hypotheses are mutually exclusive. A place well suited to a ritual burial (for the reasons of not attracting carion feeders or otherwise not poisoning resources normally used) would also be well suited to burying victims that people would want to hide. To me, a bog seems like a place that would leave little trace on the surface relatively shortly after a burial. It would, as a result, serve just as well as a means of symbolically "sending someone to another realm" as it would concealing a murder.