I've looked at many other bikes since this issue came up and could only find one other one with the same bolted-up clevis bracket but that was by means of an M10 high tensile allen bolt rather than an M8 welded stud.
All the rest have the clevis bracket built in one piece with the outrigger forgings or other sort of bracket, including other Triumphs, the Bonnie seems to be an exception. The Scrambler does have the clevis in one piece with the outrigger though.
Strangely enough this morning I had a nice ride on a friend's new Honda CBF600 Hornet and the first thing I did was to examine the footpeg fixings closely. My friend was a bit nonplussed about that and asked what was I looking at. I explained excitedly with some pleasure that his footpegs were mounted on fixed clevis brackets...
I think he believes I've flipped or suffer from dementia or something. All those lovely technical features on his new bike and I concentrated on his footpegs...