I do think, that in-universe Durykarn was noticed and Krishnarjun wasn't.
Mostly because Krishna had 1608 wives! (1600 of which he married to save them from "disgrace" after they had been abducted by a king, the other eight were romantic)
and Arjun had 4 (Panchali and Subhadra are the well known ones, Ulupi and Chitrangada are the others)
So obviously they can't be involved people thought, they're even brothers-in-law! (ignoring the fact that Draupadi is married to five men and the pandavas have other wives) (they are not monogamous)
I think Arjun genuinely loved Subhadra but there was also "I can't marry you but i can marry your sister and connect us even further aside from being (officially, in public) cousins and best friends" going on. (subhadra also loves arjun, wants to escape arranged marriage)
But, Durykarn however, 1 wife each, always together, making public dramatic gestures (so do krishnarjun but for the aforementioned reasons it goes unnoticed)
Pandava supporters made slanderous pamphlets about it