Yes I see what you mean by the explosion risk. Funnily enough my father was a furnace controller at a council incineration plant but I can't remember him saying anything about the risks of sawdust although I can remember standing with him listening to the aerosol cans going bang.
It does seem strange that sawdust shouldn't go in the composting bin although I suppose the worry there is people dumping treated timber dust and chippings. A friend of mine was also warned about putting used animal bedding , which in his case was wood based used for his rabbits , in the compost bin too which to me seems even odder . I think I've mentioned it before that I've visited a local compost farm and have seen council vehicles dropping off garden waste the majority of which seemed to be evergreens , pines and laurels .
The comment about peeling vegetables outside so that it's garden rather than kitchen waste strikes a chord too. I do house and garden maintenance and see that sort of thing all the time in that some seem to consider anything from the garden can go in the brown bin . This can include not only vegetable matter but also plastic plant pots , bricks and all sorts of junk
