But what was Adagio to Beethoven? There no metronome markings back then, slow could have been anything it's all relative. If you examine Beethoven's use of metronome markings, they were always really quite fast, even for slow movements.
Personally, op 27/2's Adagio I find to be really quite boring. I don't want to be sitting in concert listening to that first movement for 10mins, however glorious the harmonic progression is. I don't think it is musical to place it just so slowly, it seems to just be a false tradition of sentimentality. Now, perhaps Schiff does take it too fast, I don't know, I haven't heard him play it, but really, it shouldn't be too slow.