So I'm using the sportsbrooker BetInAsia, but if I bet on say O/0.5 goals and the outcome is determined really early, I still need to wait until the end of the game before the bet is settled.
Yes, that's correct.BetInAsia is a broker, not a bookmaker.
Even if the outcome of your bet (e.g. Over 0.5 goals) is decided early in the match, BetInAsia, as a broker, won't settle the bet until the game officially ends. That's because they simply forward your bets to professional bookmakers like Pinnacle, and those bookmakers don’t offer early settlement or cashout all bets are officially settled only after the final whistle
Ok even if all of the bet is made through Betfair which settles bets during the match (I know since I used to have an account there), BetInAsia still only settles the bet after the match. I guess they just do it with all bookmakers and exchanges regardless of what they do.