Sometimes a loud boom is created by reforming the caps with A/C. Ask how I know.Agree 100% with your post. AC capacitors discharge themselves because they are AC.
DC capacitors on the other hand are an entire different animal.
They actually store current and need to be discharged manually by shorting between the poles with a shorting rod like a screwdriver for low voltage caps. (480v and below)
High voltage DC caps may require grounding rods that can be 8’ in length and flash suits to discharge.
Sounds like a high power rifle shot going off when the grounding rod gets close to the pole which generates an arc that is brilliant enough to cause vision damage if not wearing the protective gear.
Quite the experience to do that.