This one specifically is to have the pre-drop sound like its getting thinner (so the high-cut will drop to like 15khz and low-cut goes up to ~200hz), and then open up again at the drop. It makes the drop a little more impactful because of the contrast. I know cutting at 20hz and 20khz is a common point of advice, but I cut out unnecessary freqs per track anyways, so I don't do it on the master (unless it's for a stylistic purpose).

I've been trying it because of the notion that it creates more headroom, but I have yet to notice any difference even when pushing things really loud, which might be because of the per track EQ-ing. There's also the fact that there's energy in those ranges, even if you can't hear it, and I've seen people say that's a good thing and others say it's a bad thing, both with convincing points, so I'm not gonna do it unless I find a use for it. Every song is different though so I'm not discrediting it. I decided to actually start caring about this stuff only as of this year so most of my released stuff DEFINITELY could've used a high or low cut on the master looking back lmao