Just switched Gen 3 to 4 and have noticed the noise, but when I think back to when the Gen 3 was new, I thought it was quite loud. I even recorded it and showed the LBS, and they said that was normal.
My opinion is, we are much more sensitive to noises on a new bike. I also hear a noise coming from the new forks, but all the tests show it's working fine.
One more possible reason, is the gen 3 had internal gearing, where the gen 4 does not (the 14T chainring vs 36T)
All the motor comparisons I've watched say the Bosch is the quietest, but still makes noise.