Chris, in order not to speak aside of each other...YOU are not possibly THE CHRIS (Flint) having written the excellent "Actions" survey?
Anyway...the Wheatstone 1944 patent papers presents two action models, one Fig 3,5 and 5A with a fork post and axle/rivet, another one Fig 16 with a loose saddle connection lever "riding" in a hole in the post. This later model is part of the actual patent being exposed in the text p8 as "my sixth improvement" and the motive being that "the lever can be instantly detached from its bearing to be examined, and the workmanship required is less"
None of these two obviously is the type we mostly are familiar with as the "riveted Wheatstone action" in the period ca 1870-1930s

Despite not being the same the Wheatstone (first Fig 3,5) and one of Rock Chidleys and Wim Wakkers basically should work in the same way and have similar stability and friction characteristics.

Did Nicholds use a similar fork as well? I have seen some Nickolds instrument with a hooked action also.

And yes! - I see no reason meaning that there is any basic difference between common Wheatstone asymmetric riveted model - Case and Jones similar variants. One detali has struck me - I have two Case trebles and the levers on these are dead straight while I think all the same size Wheaatstones I have had have some bent or S shaped levers. This is hardly a crucial matter BUT a straight lever no doubt IS preferable technically. I haven't investigated the possible cause of the difference. With many anglos having a hooked action ( Lachenal type) the U-shaped short levers on 3rd row can be a real nuisance by instability however.