Middleton Press are admirable for providing a good sweep of history for a lot of routes with a lot of interesting pictures that many of us wouldn't have had the opportunity to see otherwise. I've never found their captions disappointing, and whilst I'm glad that those with a deeper knowledge are happy to contribute further information, perhaps they might consider a less supercilious tone when discussing an excellent series.
I have a few of their books myself and concur with what you say; however they are not what I would term scholarly and, I doubt, are intended so to be. My recommendation remains that anybody wishing to establish 'facts' uses either original documents or more than one secondary source.
In no way is the world a worse place through the existence of series such as that of Middleton Press - long may it flourish!