Bug with passive skill tree when using weapon set specific passives (ID: 1.159.956.037)

So, I found either a bug or something that was never clear enough (to my knowledge, but I didn't watch every stream, Q&A, etc), and I'd like to know if this is a bug or if it is working properly.

Basically, playing a sorceress, using lightning and cold damage at the moment. Had a couple points to put, both for general tree and for weapon specific sets.

So I saw this part of the tree that I had:



So what I decided to do was: I allocated 2 points on the left side, with the fire bonuses, then refunded the 2 lightning ones, then allocated the lightning ones with my lightning weapon set and the cold ones with my cold weapon set, like the following:

Set 1:


Set 2:


Then the plan was to refund both fire passives, since with both weapon sets, the northern part of the tree would still be allocated, set 1 using the lightning path, and set 2 using the cold path, but the game does not allow me to refund the fire path, because it would "disconnect" the tree, even though both would still be connected.

So the question is if it's intended like that, and you can't split for weapon sets and then "rejoin", or if it's a bug, or never thought of.

And if the answer to this question has already been said on an interview or something, sorry for the post.

Thanks.