It's really tough to be able to help with advice from the small amount of info we're able to share through posting here, since we don't actually get to meet each other's children or experience the same school ourselves etc. I may be off in what I'm reading, but fwiw, here are my random thoughts -
The first thing I wonder is what are your observations about how he fits in? Not whether or not the other children are where he's at academically, but have you watched him at playtime, on the playground, etc when the kids are left to just play? Does he try to interact with the other kids? Or does he sit off on his own and never make any attempt to play with them? Is he hanging with the caregivers because they invite him to, or is he seeking them out even though they are trying to help move him into a play situation with the other children? Does he seem happy or not at ease when it's playtime?
Your ds is doing fine at home and he's clearly ahead in some developmental milestones, so you're experiencing him from the perspective of parenting a gifted child. He's in a preschool that gives reports based on age-typical developmental milestones and doesn't attempt to offer help with advancing kids academically beyond where there age is typically at. You're also getting feedback from the school that your child isn't fitting in socially with the other kids as kids his age typically do. That might be because he feels different due to intellectual mismatches, but it also might be because he's shy or uncomfortable in the specific preschool environment or because he has some type of challenge as DeeDee mentioned. Without knowing him and being there, none of us can really know what's up. Having parented three kids through early childhood, two of whom are 2e, and one of whom is just simply confusing (lol)... my experience was that as a parent, it's easy to brush aside what another person notes about your child if it doesn't fit the child you know and think "oh, that's because he's gifted and they don't get it" or "oh, that's because he's orange and they are into green" etc. Usually that's all that it is, and that's probably all it is in this situation too. OTOH, we've been in similar situations (but different issues) with two of our children - one our dd10 when she was in preschool and one our ds12 when he was in 2nd grade- situations where we were receiving input from their teacher/caregiver which didn't make sense to us so we interpreted it as the teacher/caregiver not understanding our child when in reality, the input was important input that we didn't see for ourselves at the time. With both of my kiddos, like DeeDee, I sure wish I had known earlier to trust that there was something going on and not just write off what the teacher/caregiver had to say.
Please know I'm not suggesting that there is anything going on with your ds other than his simply being gifted or possibly being in a daycare that's not a good fit for him or possibly simply because he's still very young. I think I'd personally consider looking for a different daycare, try a switch, see how he gets along in another situation with different caregivers. If he is still having a tough time fitting in socially then I'd look into it further.
Best wishes,
polarbear
