For Collector, I do see top runners dash into collector before screaming, so that they take dmg during screaming and be able to attack. This is legit (as in "not a major glitch"), btw. But seems to require good timing (e.g. I get 1-2 out of 10 when I try it).

NVM I found this guide which isn't mainly for this purpose but did explain the concept of "storage" in its FAQ. https://www.speedrun.com/hollowknight/guide/4e1dp

FWIW, for the benefits of new comers, I wished there could be one single guide to explain the rules and the glitches in finer detail (and made easier to find).

Thanks for the reply, KC_Speed.

I tried to understand the major glitches (I noticed inventory storage), but didn't find a guide for such explanation.

Is there resource explaining what each major glitch looks like and how they actually work?

I'm sure there is a reason. I'm guessing it's banned by the rules. But I don't see where in the rules that this is banned. Will be great if anyone can enlighten me.

Rules I checked: https://pastebin.com/VtzvMpyW

Example speed run (P5 NMG #1):

The inventory scream skip:

For example, Soul Tyrant's scream wasn't skipped in the above speed run. However I just tried on my xbox that the inventory skip can be done with my dumb hands and get in at least one hit, so I imagine multiple hits in the hands of a top speed runner.