Thunder Web debuff incorrectly increases Action Speed, instead of decreasing it

The description of the Thunder Web debuff, inflicted by Pale Seraphim and a few other monsters, states "You have reduced Action Speed and take Increased Damage". But visual observation and the character screen stats both agree that it actually increases action speed by 15%.

Character screen comparison:
https://ibb.co/MvDtbQD
https://ibb.co/ns9spr4F