It depends who these people are and the context of when they are saying it.
I always tend to compliment the abilities and traits in the kids that I know. If their parents are interpreting it as more than that because they hear it repeatedly from other people, I wouldn't know.
My kids are young, the oldest is 5. I always get compliments on general things for all of them, like their behavior and personalities. For my oldest, it's a little more specific, because she's in school and piano lessons. So I'll hear things like, "She's extremely creative and good at drawing." in addition to the personality stuff. Or, "She's progressing wonderfully in the piano" (why wouldn't she be? we practice every day) This makes sense, her parents are both artists and musicians, and she's as good at drawing and playing piano as the next kid-maybe better than some. Whatever. It's just a nice thing for people to say.
Now, has a series of experts approached me to do studies on her because her teacher reported her outrageous advanced art and music accomplishment when no other kids have even been able to hold a crayon yet or plunk some keys so she must be a prodigy? No.
So ask yourself to what degree the comments are rooted and intended. It almost sounds like you think your kid is not all that great from your tone, but I'm sure that's not what you mean. What do you mean you feel like you're deceiving him? Like you compliment him even though you don't really think he's great? And it feels deceitful because maybe he isn't great? It's not deceiving to praise your child even without proof that they are the biggest super talent ever. I really mean it when I tell my kids they're great at something, and I don't know if they're great compared to every other kid in the world.
There are ways to compare him to information on other kids if you're unsure if he's really superior or not, but the fact that he's really great compared to some kids at some things is probably true! Kids have different strengths and some are gifted. I always got comments on being really advanced in art when I was young, and they were true. Compliments I give to other kids about their strengths are true. What people are saying is probably true! The most important thing is that you think your child is great no matter what they do.