Croatian NT team is corrupted and is in the hands of Dinamo Zagreb's president Mamic (and his brother).
So, when a player needs to be sold or hyped, he is called into an NT team to get his price raised.
Halilovic wasn't that special in Dinamo at all (he was more like a spoilt and talented kid, and the owner Mamic gave him captain's armband and allowed him to do whatever he wanted on the field, no matter how selfish or poor he was, because he knew that he will earn a lot on him. In the end, Dinamo earned much less than they expected from hyped-wonderboy Halilovic).
He is sold now, so his playing in NT team isn't connected with sales anymore, but still, we should judge Halilovic's abilities only based on his displays here in Barcelona B. His plays in Dinamo, captaincy, and playing in NT team were just a well played show for potential buyers, so don't draw too many conclusions from that.