I think there are 2 main reasons:
Oscar Mike wants to be befriendet with everyone and to help everyone. So he goes onto Attikus nerves too and want to be friends with him. /Spend freetime together)
Oscar was in the cloning tank until his body was the one of a mature soldier.
Most likely these full grown clones are only teached most fundamental things: war, shooting, how to wear the armour, eating, speach.
I think the fine nuances between male & female (behaviour, cultural roles, references, stereotypes) are not teached by the UPR clone-instructors.
OM has to learn these things by himself, and well, that could take time…
Also OM picks most stuff up from TV and does not understand most references. (WF-lore)
So in his world he can be a great Femme Fatale, since he does not know that the Femme Fatale is a classical female role.
At all, its just a roleplay. I can be a male Ork warrior, and I´m amazing at it!
I think this makes him on of the most lovable characters in the cast