Quote Originally Posted by KageTokage View Post
BLU's Magic Hammer has the same description/property.

It just means you can cast Phelgma then immediately start casting another spell the instant it goes off (Barring any potential animation locks) as it does not trigger the GCD.

I'm unsure of why they decided to make it that way instead of just a OGCD, though.
Doesn't magic hammer have a (short) cast time? It's probably masking the GCD since the GCD already starts the moment you begin casting a spell. You can see the same "does not share a recast time" description in other moves like gnb's gnashing fang and sonic break or even machinist's drill (well it's more that it says it shares a timer with just bio blaster) and they all trigger the GCD as you would expect. Phlegma is gonna trigger the GCD for sure and you're definitely going to notice when it's instant cast.