The Lethal Draw Sacral Quiver

I've been testing this quiver out and I had expected life recovery flask nodes on the tree to increase the added physical damage but it seems to only take the face value number on the flask.

Is this intended? or currently a bug

If this is intended is there any other way to increase the number on the flask directly apart from quality?

Thank you

Tested and came to the same conclusion
This has to be a bug right?

What's even the point of this unique if it doesn't scale with flask recovery stats?