A great example that I found in Respecting Babies by Ruth Anne Hammond for understanding what it feels like to be a baby who is put in a position that they are not developmentally ready for, is trying "tummy time" for yourself. Like the book suggests, I laid on the floor on my back and moved my arms, legs and head around. Then I rolled over and tried the same movements. What a difference! Even for an adult who can support their head, roll over by themselves and quickly get out of that position, I felt a little helpless. Holding your head up while you're on your stomach is tough! Breathing is harder and your range of motion is totally different. Once you try both positions, you get a sense of how your baby would feel. You also have a better understanding of how "tummy time" would feel for a baby who is not ready to be on their tummy. I encourage you to try tummy time for yourself! It really opened my eyes to why it's so important for the child to be in control of their own process and how we should be respecting the baby's instinct and internal time table.
Free movement is important because it builds the child's own awareness of their body. It helps a child learn to problem solve and they prepare for the next step. When a child is given ample time to move freely, they are building muscles and practicing important skills that they will need later on. Adults may see a baby on their back, who seems to be struggling to roll over onto their tummy. Their instinct, and my first instinct, would be to roll the baby over! When you really think about the process the baby is going through, you understand why rolling the baby over isn't benefiting them in the long run. Struggle is a beautiful thing. In the baby's struggle, they are learning and getting stronger. Babies are determined and they will get to the next step but when they are ready to. When they accomplish their goal, whether it's rolling onto their tummy, crawling, balancing, walking-- on their own, they feel the same joy that we as adults feel when we complete a hard task. Putting a baby in the position they are working towards, takes away from that feeling of accomplishment they will have once they finally do it for themselves at their own pace.