I had my 09 328i in for the warranty lifter replacement, I had originally taken the car in for the whining noise as described in the first video, my car was not as loud. SA said same thing that it was normal engine noise.
When I dropped off the car for the warranty work I asked the SA to take a drive with me this time to have him hear the noise, of course he said the same story that it was normal engine noise. Interestingly enough when I picked up the car after the lifter work the SA told me they had reviewed the alternator and tested it and that it was in fact failing and BMW would be replacing it under warranty.
So just waiting for the call now to say the alternator is in stock, I'm really looking forward to this replacement, the whine/howl is intolerable.
If you're still under warranty keep taking it back, it's clear these alternators are far from perfect and expensive to replace your self.