/effect defaults to 30 ticks for instant effects, instead of 1 tick

The bug

When using /effect with an unspecified duration, it's supposed to default to 30 seconds for normal effects. This works fine. However, it's supposed to default to a single tick for instant effects. This does not work, instead it defaults to 30 ticks.

How to reproduce

/effect @s instant_damage

Expected behavior: You take damage once

Actual behavior: You take damage four times and die