I saw a review of the XPS 13 9380 mention the problem.

Googling shows it has been a problem since at least the XPS 9530 (2013). I notice it intermittently on my 9570 depending on load/activity.

If they can't fix it after 5 or 6 generations, I wouldn't have much hope they will ever fix it. Apparently Dell test that the sound levels are below some limit, but that means can still hear the noise.

TBH I never had that problem on the 9360 (in over 2 years) - YMMV. Knock on wood though as I had to replace the battery and the AC adapter died.

Anecdote of one but my one-year-old XPS 13 doesn't have it. Returned the '17 model it was terrible.

Anecdata: I own a 9380, and it doesn't have this problem.