If you had a bigger hand you could place your hand around more notes and not have to blind jump....i get that. My left hand has to do things it doesnt like all the time! Haha....yeah if you listen and play your left hand by ear youll get it done. I wish i had giant hands too. Not too giant though.
Its not about being blind.. or jumps (maybe kind of jumps)..
To provide an example, which is a little contrasted against rachmaninoff...
Supposed you are to play a single figure from chopin etude 10/1 - perhaps one of the slightly tougher ones.. CFCF or something (bar 11). The fingering here (for me) is ||: 1245 :|| which creates a musical shape over the CFCF that spans up an octave. If you fingered it ||: 2415 :|| (yes I know thats really unlikely) it would be REALLY difficult to generate a smooth flow in the right way, because of the wide thumb pass in the middle of the figure. Physical legato would now be totally dependent on pedal technique and you also wouldnt have a physical connection to the piano which means that you're going to have to "land" on the thumb with nothing less than an absolutely immaculate touch to avoid an unintended accent on the thumb.
In the concerto, there are places that someone with hands the size of rach would probably have used fingers like that, just 12345 type things (single hand position over a wide interval I mean).. and as a result had an easier time controlling the shape of the phrase.. you can kind of see it in the way its written (compositional idea/intention).. By that I mean ideas that are drawn out of your physical capability. You compose what you can play comfortably.
Look at this bar

See how the middle line is almost chromatic? so if you over do the pedal you get BLURGSGHELKJHD. So what about the minums in the RH, the A and F? they have a tenuto. So either you have to pedal the legato, or you actually hold it, and either way is total balls for trying to play the middle line.. either the sound is BLURGSGHELKJHD (too much pedal) or you hold it and you hand is contorted like its been through a meat grinder - I can play it totally physically legato which one flowing hand position (freakin slowly) if you place 4 on the E melody note, 3 on the C - last not of the bar - and 1/2 on the C,A on the first beat of the next bar. The reason I play it slowly is not because I can't get through it faster, its because the movement is VERY precise to avoid injury (the stretch is very extreme for me) so it needs to be very well rehearsed before I just let rip there.
Alternatively, I do it by placing 5 on the E, 4 on the C, and 1/3 on the C/A - which is a hand position shift which disrupts the use of a single flowing shape, and now I MUST use a pedal legato to generate the same effect, which has to be fairly precise to avoid the BLURGSGHELKJHD coming out of the middle line... its a different challenge.. It's a bit of a battle to balance a respectable amount of pedal to keep the feel of legato melody lines while using a super delicate touch in the middle voice to not end up with all the chromatic dissonant resonances overpowering everything else.
SO you know, whatever.. its not that the bar is anything special, its just one of many challenges, but rach hands would definitely have done this easier i think.. I mean, rach would've been precise about it, but hands that size could get away with less precision I think and still navigate the notes... or perhaps use a technique that I personally consider easier to execute that what I will probably have to do to get it to sound how I want it to.
..
Ultimately I doubt I'll do it physically legato, my point is not that it should be.. just that rach probably could have done it that way if he'd wanted to, without nearly the trouble it would cause anyone with small hands.
Edit:
Maybe thats what you meant by "blind jump" anyway, i'm not really sure - i guess I mean that its not about hitting the right notes, the size of my hand isnt a concern as far as getting to the right key accurately, its level of touch control required when you get there..
Also, started mov 3 last night. Hardcore.
began here.. and beyond... seriously one of the most exciting passages in the entire repertoire for me. Gives me goosebumps consistently this bit.