No, the 3rd and 4th Gen both have the same buffer. Not sure about the 1st and 2nd Gen, but the 1st Gen had a 7 minute buffer, I believe.
Also, if the buffer size was increased, it means that the HDD would have to spin for longer in order to fill it, which results in a greater probably to skip during a shake. I think the remedy is to give it a bigger buffer, but also increase the HDD speed. That way, it doesn't take 50% longer to fill a buffer that's 50% larger.