Don't you mean the *London* symphonies? AFAIK, Szell only recorded a couple of the Paris group.George Szell was capable of conducting well, at times, yet I often find his conducting too stiff, such as in his Haydn Symphonies (& particularly his set of "Paris" Symphonies), for example. & it both surprises and perplexes me that others, who are bigger Szell fans than I am, either don't hear this stiffness, or don't seem to mind it.
But I agree about Szell's Haydn. I wouldn't necessarily call it "stiff", but to my ears, it's utterly lacking in charm - Haydn played through clenched teeth.