GNB ideal Skill Speed?

[mosaicex]

Go for 2.39s if you have high ping, 2.4s and slower if you have good connection

Can you explain the reasoning for this?

I've been doing some napkin rotation mapping and I found out, as expected, that GNB works best at baseline GCD (2.5 seconds) due to how Gnashing Fang and Sonic Break recast timers work, guaranteeing they (plus 2 Burst Strikes) will both line up with every No Mercy buff window (and 60 seconds raidbuff window). Pic related

https://i.imgur.com/IwAZ6uC.png

As you can see, everything lines up pretty nicely.

Of course having 'some' skill speed wouldn't hurt due to fights' downtime and such.
But I still don't really see the benefit of having 2.4s GCD.

Edit: After having a look at it again it seems that 2.4 seconds GCD might really be more optimal after all, assuming 100% uptime, of course.