Belt or Braces or Belt and Braces . . .
Interesting that the 2 UK marques who gave us through-stud vertical twins - AMC and Royal Enfield - ended up with worse reputations for reliability than the NoTriBsa triumvirate, even though the formers' designs were in many ways purer - and far truer to the sporting genre of the fast singles. Easier to put together too, with separate cylinders.
Haven't seen a through-stud engine rip its whole top end off (in road use that is), although they can sling their head gaskets into the hedgerows and leak Olympically from the barrel/crankcase joint. Conversely, loads of non-through-stud engines have head gasket failure AND stud/bolt trouble (like our As), and also barrel base stud/nut/flange trouble (like our As) . . .
Ergo, I reckon through-studs are better in principle as there is only one lot of fasteners to fail, and the loads are evenly distributed and shared. But I also reckon the engine and its castings have to be designed that way.
Ergo, 'straps' are good for engines not designed for through studs or bolts, just as, we hope, braces hold when the belt has long gone. But in a motorcycle, head steadies made of sturdy farmyard scrap iron instead of pretty bits of useless shiny stuff, do much the same thing. The frame is stronger than any strap could ever be . . .?