Devs is this a bug or intended?

[HiNMity]

I just got my first Tier 11 skill gem and used it on Whirlwind Lance and tested out how it interacts with tornadoes and elements. Mostly its the same as Whirling Slash, which I know is intended, but if you cast Twister at it and Twister picks up an element on the way it doesn't split into new Twister, just collapses the Whirlwind. This happens as well even if the Whirlwind is also the same element as the twister, example a fire Twister into a fire Whirlwind.