I don't think shakehand is a shortcut, because when I started playing, I was using both grips and penhold was easier and more confortable for me (only for me, all the club members were playing shakehand).
I'm sorry, I wasn't clear enough. Shakehand in itself isn't a shortcut, but in comparison, if you as a coach want a certain student to reach a certain level, it will take longer for that to happen with penhold.
I think the learning time depends on the training hours, the coach and talent of the player
Yes, of course, but it also depends on what technique you are learning.
Let's say the coach wants to bring a player to World ranking No 1500 (just a random example). Let's also assume the player and the coach are the same people in these two examples (same skills, same "talent". Everything is the same except the technique taught)
Same coach + same student + same goal WR1500 + shakehand = 5 years to reach
Same coach + same student + same goal WR1500 + penhold = 7 years to reach
This is not my idea, it's a theory from within the Chinese coaching system. I read it in an article over here years ago:
http://home.covad.net/chunglau/ttindex.htm
The site is an index of English translations of Chinese TT articles. I can't say which article the snippet is in, because I'm afraid I've have forgotten (and there are just too many to sift through to find it quickly). In any case, it's well worth having a look at the articles. They are great reading if you're interested in table tennis and some of them give great insight into Chinese attitudes towards practise, tactics and reading and playing your opponent.
So I still believe one of the reasons penholders are slowly disappearing at higher levels is about pure economy - it simply takes much longer to achieve the same results as with a shakehander.