Yes and no - Christ expects you to believe him, via those he has sent. And no, there are explanations to those who listen as disciples to the Church. It can be explained to the one believing him to any level of understanding needed by the individual person in his desire to know.
The declaration by God that there is free will is “good news” that is part of the big picture of Christ.
**Well, free will is not clearly outlined as Church doctrine because it is assumed that people would believe in it already. **
Now, to you, wanting to understand it, as Thomas wanting to put his hand in the side of Christ before going “whole hog for Jesus” and only then saying “My Lord and my God”, for you there is someone like Thomas Aquinas - you have spent 3 weeks on this thread, now, and in that time could have read far enough in the Summa Theologica to have come across several of the minor explanations of free will, with much of the sub-strata for taking the explanations seriously. (Summa is here:
ccel.org/ccel/aquinas/summa.toc.html )
Here, at this site, you are listening to sound bites of people who know it is true, but you are somehow expecting them to give you dissertations from your replies. Well, we really don’t have time for it because it would disrupt our family and work responsibilities to answer you. But there are already full explanations. Read Thomas - you appear to have the background to handle his treatment of all of Catholic teaching. It is a cumulative treatise, so read it sequentially, even if you jump ahead to various points as you read, go back to read it in full.
OK, but Aquinas begins by assuming that freedom exists. Does Aquinas attempt to show that the world as we know it cannot exist without free will?