"Paray was strange in that he never went to concerts, listened to the radio or records, or attended other's rehearsals - so the only music he ever heard were his own concerts".
At a point earlier in his life, he must have done those things quite often or he never would have heard any music at all, much less become a musician himself. By the time he got to Detroit, I'm sure that he was working enough that he didn't need to go hear other folks. Enough is enough, you when you have to work at it almost everyday.
"Still I like his Suppé overtures disc on Mercury..."
I can't think of any reason why you or anyone else shouldn't like his Suppe disc. In fact, I don't think that he recorded anything that wasn't at least likeable. I feel that Paray/Detroit has one of the best conductor/orchestra, recorded legacies going; right up there with Ormandy/Philly; Reiner/CSO; Szell/Cleveland; Munch/BSO; Karajan/Berlin; Haitink/Concertgebouw, etc.