Vigor Mortis + Wraith Wreath's equipment speed penalty negation effect isn't working

When you drink the Vigor Mortis elixir while the Wraith Wreath is equipped, movement speed penalties on equipment such as those on the Marble Suit or the Piggyback are supposed to be reduced by 25%, but this doesn't seem to be working for some reason.

You can easily check this with the Marble Suit as Wendy with Abigail: the default player speed is 6, and Abigail's speed is 5, so if the elixir is working, Wendy's movement speed should be 5.7 and she should still be noticeably outspeeding Abigail. Abigail will easily catch up though, because Wendy's movement speed is being reduced by the full 30%, making her actual speed 4.2. You can also start walking with the wreath on and the buff applied, and while walking remove the wreath and observe no change in movement speed. And yes, I am absolutely sure I'm drinking it instead of applying it to Abigail.

Strangely, using this in the console:

ThePlayer.components.talker:Say("Speed: "..tostring(ThePlayer.components.locomotor.GetRunSpeed()))

will report that your movement speed in the above scenario is 5.7 like it's supposed to be, but it's clearly wrong, so I have no idea what's happening.

Edit: Went and doublechecked Vigor Mortis's other supposed effects, negating spider creep and the Bee Queen's honey trail. While you walk at full speed on spider creep as expected, the honey trail negation isn't working, either. Probably should have checked those before posting.