OP, your post sounds like my 3.5 year old. Low tone diagnosis. I could have written your post and his amazing PT told me that low tone/hypotonia can sometimes look like cautiousness. When I described how my son watched other kids play on the apparatuses at the playground instead of going to play himself, she explained that children are excellent at knowing what their bodies are capable of at a very young age. And that maybe he was watching other kids go down the slide and thinking it looked like fun… but realized it wasn’t safe for his body.
She does PT sessions with him at the playground and helps give him confidence, along with building strength. She is such a pro and has been doing this work for a long time.
Here’s his PT’s info, in case you want to discuss this with someone:
Meghan Rosenberg
District Kids PT
https://www.districtkidspt.com