Here is a video to stop this rattle.Same here, my 2018 has the same b pillar buzzing which is very noticeable when driving on the highways. I've narrowed it down to the seat belt height adjuster on the b pillar. I'll add this to my next round of repairs for the mobile service folks.
No it did not fix the noise 100%. Clicking still present but very faint and you have to hold you ear against the B-pillar to hear it with silence in the cabin.
That buzzing is most likely the seat-belt height adjuster - plastic on plastic slide. Both my 3 have never had that issue.I have some occasional buzzing also. It doesn't bother me.