Thank you for posting this question. It is something I have thought about for some time, so I am glad someone also feels the same way and has posted his/her thoughts in words.
I think there is a bit of truth to the statement that there are superfluous notes. I don't think it's a matter of live vs. recorded. I listened to Yuja's performance of Rach3 live, in good seating, and still noticed there are notes you can't possibly hear with the orchestra, the main melody of the piano part, and the incredible speed required for some of the runs.
A more concrete example:
Rach 3, 3rd movement, Meno mosso (marker 45 from the IMC version): I challenge you to say you can hear every note of every triplet along with the left hand accompaniment in this section. As beautiful as this melody is, the key points are the quarter notes in the RH. You often hear Lang Lang, Kern, and Agerich in their recordings blaze through these sections, almost with seemingly missing notes. More supporting evidence this section contains superfluous notes? Rach revisits this theme again a little later in the 3rd movement. And yes, the next time is with a lot less notes. Do you lose the musicality the 2nd time around? I wouldn't say so since if you ask most musicians to listen to Rach 3, unless they studied Rach 3, they would be unlikely to even discern the 2 versions of this melodic line. Musicality is not lost in the 2nd version, despite the reduction of notes.
There are many parts of Rach 3 that are literally blazed through, and although 50% might be an exaggeration, there are quite a number of notes that don't really add to the musicality of the piece. Many notes get squashed by the orchestra and the main melody, even in a live performance. The performance doesn't lose quality because of this.