I don’t have a direct quote, but I remember reading a few years ago that valve was debating how to handle bombing. They said something along the lines of not wanting to silence the bombers, but to highlight it so it was clear it was a review bomb. I got the impression they were considering things like showing the unusual spike of reviews in a different color. This sounds like it might be the results of that.
They already have something for it, when I look at a review bombed game it specifically tells me that theres been unusual activity with the reviews. I believe you cna choose to hide or show the review bombs in the settings somewhere.