Zed ult and Vlad pool?

I'm not sure if its intended or not but the "bug" is when a ult's a then vladimir presses W and goes into his pool it essentially does a "qss" like effect and actually remove the zed ult completely and no i'm not talking about the damage i mean actually completely remove the ult as soon as vlad goes into his pool as like its a 'qss" to his ult. I'm unsure of this because i know sometimes even when vladimir goes into his pool he can still be damaged sometimes; I might also have a distant memory of when i was zed and ulted a vladimir the mark would stay on the vlad and still activate the damage even under his pool but i could be wrong but if not i only recently started to see this.

In one of my recent zed games i was fighting a vladimir and when i ulted him we were both sorta confused as to why my ult mark was gone so we tested it and it seems its able to be replicated easily enough as well.

I don't mind if its intended it just seems weird to me because i think some things like fiddelstick's drain actually still damages vlad in his pool right?