The owners of the Flying Scotsman are certainly sensitive to issues of originality; they stress “significance” over “authenticity”. There are many other examples of course; Cutty Sark post fire, HMS Warrior come to mind; perhaps these things are tributes rather than restorations. As you rightly say, they give pleasure to many who would otherwise never understand the impact of these devices in our history. Jaguar Classics are the in the same channel with their D type and the E-type lightweights. What are they, originals, replicas, there are strong feelings on this. The Goodwood people refuse to recognise them as originals for racing there. There seems to be a fine line between preservation and Disneyfication. Mallard, as you mention, is certainly in the former category.
For those interested in traction engines, be warned they do not have brakes per se and rely on steam cylinder pressure through the transmission to stop ( there is a crude parking brake but it is not used for stopping motion). Together with the primitive steering, the things are imprecise at best on the road if not in the most skilled hands and should be given the widest berth possible. The saving grace is their low speed, as anyone who has been stuck behind one or more on their way to the Great Dorset Steam Fair will know all too well.
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