Wanderlust slow immunity doesn't apply to "Drowning" debuff

The River Hag in the Drowned City spawns a sphere of water. When you touch this sphere a debuff called 'Drowning' gets applied to you. This slows you significantly and instantly kills you after a few seconds. My character is being slowed by this despite having the Wanderlust boots equipped with the modifier "Your speed is unaffected by Slows"

Video: https://www.youtube.com/watch?v=ClInAU_B9oI

Debuff:


Boots: