If you think about it from a diff point of view it does make sense since he's no kid originally as he can shrink himself too so he's mom would look at him I think
That "kid" is an immortal god...And if you read the first chapters carefully the manhwa explained it beautifully and accurately with the myth...
Eros stayed as a child because Aphrodite treated him like her eternal baby and although he was way older than his form he wasn't emotionally mature because love cannot grow without being returned and Eros has not been able to feel romantic love until psyche although he was in charge of making people fall in love... That's why until he met psyche love was a game for him and he would always help his mother by causing mischief with his arrows.
I am just joking
Bro a kid just turned into a man