The bug

The advancement trigger for "effects_changed" seems to activate inconsistently when used in a custom advancement. "instant_damage", "instant_health", and "saturation" don't seem to trigger the advancement whenever the player:

• drinks a potion
• uses a splash potion
• uses a lingering potion

(However, the advancement DOES get triggered when the player uses a tipped arrow with the respective effect, or uses the /effect command to give the respective status effect)

How to reproduce

Create custom data pack(1.13 snapshot) OR place in the respective advancement folder (1.12.2)

{
	"display": {
		"title": "instant damage test",
		"description": "",
		"icon": {
			"item": "minecraft:potion"
		},
		"background": "minecraft:textures/gui/advancements/backgrounds/stone.png",
		"show_toast": true,
		"announce_to_chat": true	
	},
	"criteria": {
		"instant_damage": {
            "trigger": "minecraft:effects_changed",
            "conditions": {
                "effects": {
                    "minecraft:instant_damage": {
						}
					}	
				}
			}
		}
	}
}

(replacing the "effects" conditions with the respective status effect)
Then using a potion (drinking, slash, or lingering) with the assigned status effects.

I've included a world download with advancements and potions already made and ready to use.