You may call it restraint, I call it an inability to fit the notes into the composer’s tempi. The Beethoven concerti are a perfect example. I never realied how inept he was until I heard him try to cram all of the notes into glacial tempi. (1963 Klemperer, Barenboim, New Philharmonia). It was painful to hear...almost as though he was wearing boxing gloves...and his Goldberg? Pathetic! Simone Dinnerstein sends me to the moon with her’s...WOW!
He DID have a hot wife, though...dunno how he managed to land her...shame about her untimely demise.
He does take slow tempii most of the time. He’s a Bruckner conductor after all. I’ve never heard his Goldberg Var. but Dinnerstein makes them. sound like tinkly dinner music.