Cone of Cold and Improve Sprint BUG (WoW Classic Anniversary)

Hey everyone.
In the current version of WoW Classic, I’ve encountered a serious bug.
It’s related to the Rogue “Improved Sprint” talent in the Combat spec and the Mage “Cone of Cold” spell. I’ve been playing WoW since 2005 and still play today but I’ve never seen anything like this.
This is 100% bug, and I hope Blizzard will notice and fix it. Here is what happens: when a Rogue uses Improved Sprint, they gain “Immune” to slow effects for about one to two seconds and remove any existing slows, but they should not be immune to damage.
In the current version of WoW Classic, “Cone of Cold” is completely negated by this immunity - both the slow effect and the damage are ignored, which is definitely a bug.

I’ve attached video demonstrating it: https://youtu.be/0k0A2-u6HsE