I don’t accept your premise.Firstly, 4-4-0s are usually the bane of most modeller’s, so the fact that they worked with incredible reliability on these layouts speaks volumes for the practicality of the standards.
Secondly, those 0-6-0s could be pretty large and we’re fitted with working inside valvegear which was very accurately made, but would not necessarily respond well to lots of excessive side play, and clearances and tolerances were as fine as if the motion was outside.
Thirdly, although Heckmondwyke was designed to run a full representative service with the correct stock, other things did run on the layout at speed.
Since I don’t accept your premise, I do reject your conclusions.
That’s an interesting point, though, that MRJ by providing Tony with the opportunity to express his prejudices against P4, has allowed Iain to provide the results of some sums which show why P4 runs better, but I still think it was worthy of more than a letter. A fully fledged article with diagrams and photos would be good, especially if the S4Soc were given permission to reprint it as a handout. Some of the drawings can be found in Greenly’s “Model Railways”.