The Star Wars book Secrets of the Jedi reveals more secrets about the balance of the Force, shedding light on Baby Yoda's Force powers. When George Lucas created the Force, he was inspired by the dualism of yin and yang, light and dark. The concept of balance gradually became integral to the Star Wars franchise, especially with the launch of the prequel trilogy in 1999. Anakin Skywalker was revealed to be the Chosen One, destined to bring balance to the Force — whatever that means. Secrets of the Jedi offers further insight into the importance of this balance, and in doing so offers an explanation for why Baby Yoda and Rey possessed Force powers unseen elsewhere in the franchise.
The Disney era is gradually exploring the concept of balance, one step at a time. It has suggested balance should be seen as a distinct aspect of the Force, like light and dark. A mural of the Prime Jedi seen in Star Wars: The Last Jedi suggested the Jedi of old were sworn to serve balance, rather than the light side, but lost their way. In the sequel trilogy, Rey's new Force powers can be explained by her learning from ancient Jedi texts, thus meaning she too has learned the ways of balance — and has therefore unlocked Force powers potentially unseen for generations. Information is being drip-fed, likely as the Lucasfilm Story Group figure things out themselves, and it's developing into a fascinating new way of viewing the Force.
The recently-published Secrets of the Jedi is an in-universe study of the ways of the Jedi. It is supposedly compiled from the notes of Luke Skywalker himself, and one section naturally examines the light and dark sides of the Force. Luke knows enough to associate the Prime Jedi with balance, although he doesn't appear to make much of that knowledge, instead ascribing to the traditional light and dark dichotomy. He does, however, give some fresh insight into balance that adds a new element to the discussion.
"Using the Force properly is all about finding balance. And some Force users, particularly Force-sensitive children — known by the Jedi as Younglings — are able to tap into its energy without an obvious alignment to either side. The Force simply flows through them in its purest form. Based on the constant struggles I've witnessed between the light and dark sides of the Force, perhaps their innate neutrality can teach us all a valuable lesson."
George Lucas' concept of the Force was heavily influenced by Buddhism, and there's certainly an element of Buddhist philosophy in this, the idea that children are more naturally attuned to the world than adults. The idea can even be seen in the Christian tradition as well, with Jesus teaching, "Unless you change and become like little children, you will never enter the kingdom of heaven." In the Star Wars universe, Luke Skywalker suggests this is because children are inherently neutral, centered and balanced in the Force, and that they only become aligned with one side or another as they age. This would explain why Baby Yoda demonstrates the same Force Heal powers in The Mandalorian as Rey does in Star Wars: The Rise of Skywalker, when this distinctive form of life transference appears more linked to balance than light or dark.
This also potentially explains why Yoda was the wisest of the Jedi in Star Wars. It wasn't just that he had a phenomenally high Midi-chlorian count, exceeded only by Anakin Skywalker; it was also that he was a teacher. Yoda spent time with the Younglings, training them and teaching them, and like all the best teachers he also learned from them. Yoda was the only Jedi sensitive enough to the Force to sense a hint of Palpatine, aware of a "nothing" where Palpatine had concealed his presence.