I can absolutely agree to that.I wish I had put it this way, bankroll management is "optional" to anyone that isn't trying to do this as a profession. I agree understanding it can be helpful, and segregating funds can be helpful for non-professionals. But it surely isn't required. It's just fine to choose to play whatever one can afford and risk losing it all so long as they have other sources of income.
Professionals just don't have the luxury of other sources of income, therefore bankroll management is vital to understand.