Machinist feels pretty good now.

[Semirhage]

I think he is referring to the inbuilt 0.5s GCD lock. Not the animation.
Every OGCD ability had a 0.5s lockout after pressing it, people double weaving during hypercharge windows are using 3rd party programs to remove that lock.

Close, but not quite.

Let's say you have 200ms of ping. When you use an ability, you enter a mandatory 0.5s animation lock. This is true for all abilities, GCD or off. Your client says "I'm using this ability now!". That hits the server 100ms later. The server then says "okay sure, that ability isn't on cooldown and your job can use it. This looks okay. Use it." Let's say it takes 0ms for the server to say that, even though there's still a tiny amount of time there. 100ms later, your client gets the thumbs up. You're now 200 total milliseconds into your 0.5 second lock, so you've got 300ms to finish out before you can queue up another ability. Makes sense, right?

Except that's not how FF14 works. FF14 takes that request 100ms in, then replies with a packet that takes 100ms to get back. You're now 200ms into your animation lock. FF14 resets your animation lock back to 0.5 seconds at this point. So your *actual* animation lock is 0.7 seconds. It's 0.5 seconds + your ping, due to this reset. Stupid, right?

Those third party programs don't remove the 0.5s lock (I think you could set them up to, but they don't by default). They instead ignore the instruction to reset your animation lock, making your client behave like every other professionally-designed MMO does with an internal animation lock that doesn't artificially double tax you for the sin of not living in the server closet in San Francisco.