Rank 3 same as Rank 2 Alchemy formula Greater Flask of Endless Fathoms

Rank 3 of Greater Flask of Endless Fathoms requires the same mats as Rank 2, and only produces one flask, the same as Rank 2. What is the advantage of attaining Rank 3?

it actually gives you a CHANCE to proc extras, just like in legion it isn’t guaranteed

As usual they are laughing at us