Developers don't reply here and they are mostly just fluent in Japanese anyway, so wouldn't understand your post. There are community teams and GMs but they rarely post here either.

Recast is an easy thing to understand. It's the time it takes to be able to re-cast it. "Recast" is the same thing as "Cooldown" but is not necessarily the same thing as "Global Cooldown" or "GCD".

The reason people need to use "GCD" is because a lot of things share this same "Global Cooldown" and it's the way you would normally explain it in other MMORPGs as well. Any other term doesn't properly articulate that it's globally shared.

For the ones that aren't shared, you could really use Cooldown and Recast interchangeably and people would probably understand what you mean.

The concept of a Global Cooldown I don't think is really explained. I think you just sort of "figure it out" from playing when you press one attack and the other is unavailable as well. However, I can give you an easy way to distinguish the two:
  • GCDs are Weaponskills or Spells.
  • Non-GCDs (with unique cooldowns/recasts) are Abilities.
If any Ability actually shares the GCD for some reason, it states this extremely clearly in the tooltip.