How could the Vong exist and not be a part of the force? When the force exists in all living things and binds the galaxy together.
At the time, I was captivated by the mystery of the Vong. Their seeming absence in the Force was absolutely intriguing to me, and I was dying to know what the explanation was. Then it was revealed that they’d just been cut off from the Force by their living home planet. After all that build up, I found it a completely underwhelming revelation. And it doesn’t really square with previously established lore. Ulic was also cut off from the Force; he didn’t become a living void as a consequence. In hindsight, it comes across as an Abramsesque mystery box.