the -ms likely doesnt show it because its a completely different type of bonus codewise (to make sure u can exceed the max movespeed cap). likely simply the command has to be reworked a bit, but the ms of thirst works.
I am well aware of the hardcoded limit of 522 ms, however if you read my reply then you'll see that I said I didn't just go by that command but that the hero really didn't appear to move any faster with the buff.
If however you say that it does work, then I'll assume I was observing something incorrectly.
I had tested it and didn't notice a faster movement, but if you confirm it's working then I dont have much reason to suspect otherwise