Thanks everyone for your insights and experiences! As the mom of a singlet- it's not always easy for me to know what other 3-4 yos are doing.
I will continue to encourage him to communicate with the other kids and adapt to their interests/games too.
. At 3.5, younger even he liked to stand on jungle gyms and play toll booth he wanted to do the whole thing, and few kids would get it, we would constantly tell him to explain what he was doing
sounds very similar to my LO! He has this great imagination and creates games with rules/ideas of how things work...He complains when the kids in preschool don't want to play radiology with him, and I often need to explain he should use a different word, maybe playing doctor or hospital...
My LO is very verbal and physically advanced, and bossy. sigh. a joy for me, but maybe hard for some kids to understand yet. He is fun, and your posts give me hope that it's just a normal thing for a 3-4 yo.

thank you!