User blog comment:StoryGirl83/Elemental Attundement in the Test for "The Elementalists"/@comment-35568572-20181103110754/@comment-28520869-20181104111730

This is from their blog about the elements:

Jessica: So when I was a wee child attending Chinese school (shoutout to all the Asian American kids who had to go to Saturday school!), I learned that Chinese words all have core components called 'bushou' -- wood, heart, power, etc. During Elementalists brainstorms, we riffed on the premise of having a core something as the base for creating meaning, or in our case, magick. We settled on the classical elements as the foundation, and threw a few of our own into the mix as well. To perform magick, you have to channel the elements, and of course, everyone has an affinity to one or two -- kind of like having a college major, but also general education requirements!

so it does seem it was their plan to mix and match a bit.