Bankroll management is not a gambling strategy, rather it is a finance management strategy to prevent the gambler from messing up his finances while gambling and that involves having a budget. Every real gambler, most especially sports bettors have their unique strategies that they exploit to bring home wins and these strategies are subject to change overtime. However, having these strategies are not guarantees for being profitable and that is why we must put a financial benchmark on our expenditure on the casino through good bankroll management practices but in reality, it is not a gambling strategy.
You quite made some level of sense, it's really not a strategy to win as most people do misinterprete it but it also a strategy to stay gambling for long which at the same time ends up, to be a stand point to facilitate wining in gambling and I guess that's the most reason why it's misinterpreted to be a gambling strategy. The real sense, should be financial strategies for a long lasting gambling experience and not to ruin your whole gambling experience with lossing more than you would be able to handle and then crash out, it really protects the ideas of winning.