What you deposit is already intended for gambling, so whether you go all-in or divide it into smaller bets, the reality is that bankroll management won’t change the odds. It just adds an extra layer of stress in making decisions that, in the end, won’t really affect the outcome of a luck-based game.
Bankroll management is not always about what you've already deposited, it's about the budget you've set aside for your gambling and how you can work on being moderate with your gambling allocation so you don't allow your emotion get the better of you and push you to just flow by the trend of the urge you're feeling which can lead to gambling in an irresponsible manner.
For sports betting that's not completely a luck based game, even though you will need to just use an amount for the game you're playing, for the fact that you will be doing it for the long run will require that you implement a proper management plan in place so you don't find yourself losing more than you're winning. At the end, the goal is to ensure that you're in control of your gambling and can control yourself when it appears as though you're overdoing it.