I think the editors' politics are pretty much irrelevant. Motherwell had his own publishing business in Perth and by all accounts was a bit of a lad in his youth. His 'scholarly approach' so lauded by Child and others only came in later on as an afterthought. There is some evidence to suggest he was 'mediating' just as much as the rest, well perhaps not as much as Buchan. His later approach is certainly the beginnings of a proper scientific approach in line with Ritson, but I can't help thinking there was at least some hypocrisy in there. When he was younger he is on record as having bragged about his mediations to his mates in the pub. There is also some evidence of the people he paid to go out and collect doing their own mediating. This has some similarity with Scott as some of those who were sending Scott material were also mediating before it got to him.