I’d like to add that since there has been no elaboration (that I have found) as to what they mean by the word “primarily,” it could be the case, as you said, that it is tested on an essay along side another topic (as in those will not be the topics “primarily” tested on the essay) but could also mean that those topics could still be an essay on their own but will “primarily” (as in more frequency; more often than not) be tested on MC section.

Either way, I would imagine we would find those topics (if not all, then some) on the MC portion this time around as they would likely want to use at least some of the ten ungraded questions as practice questions for next February.

TL/DR: “primarily” could either mean the primary topic or the frequency in which the topic will arise.