In icons.png, the same position is used for absorption hearts while poisoned and the flashing afterimage of Ice hearts when being damaged.

Steps to reproduce

1. Download and add the resource pack below to your game
2. Make sure your game mode is survival or adventure, and cheats are enabled
3. Use /effect give @s minecraft:absorption
4. Use /effect give @s minecraft:poison
5. Observe the appearance of the absorption hearts
6. Use /effect clear @s
7. Now stand in powdered snow long enough to take damage
8. Observe that the appearance of the flashing hearts appear the same as the poisoned absorption hearts from before

Example images are below