Actually, yes, Sorabji is pianistic, and obviously written by a man with great knowledge of the piano.
Primarily the only new difficulties, aside from the different style of harmony which one has to become accustomed to, are -
Huge leaps exploring great sonorous range, involving dense chords.
New polyrhythmic difficulties.
And of course in his most famous works - the extreme length.
The thing is, also, that I admittedly don't like the music very much, and don't think the OC is particularly worth playing other than to prove how great a sightreader you are.
Even with these difficulties considered, none of them have extended concentrated demands on dexterity that , in particular, the Left-Hand Godowsky studies pose.
And anyone with a good grounding in the Godowsky studies should be able to adapt much quicker to the dense fast chords, leaps, and polyrhythmic elements in the Sorabji than it would take a Sorabji specialist to develop the new levels of digital dexterity to master, in particular, the left-hand difficulty in Godowsky works.
In the end, even if they are around the same level of difficulty, the Godowsky studies are great music to listen to and will always appeal to a much wider audience than music with less tonality, and will also always be a more competitive arena in which to compare pianist's techniques.