Nobody is promoting fasting per se, like full blown IF. Just pointing out that if you're trying to optimize the fat burning/lipolysis of AM cardio upon rising, don't spike your insulin before doing it. Most people have no idea high dose leucine is like drinking pure glucose in terms of insulin response and that is clear from what people post. You're not doing "fasted cardio" if you do this. That was my only point.
Am I saying it's bad to drink BCAA before or after cardio? No. But you won't go catabolic by not having BCAA and you WILL burn more fat without it. Personally if I get up at 4:30am to do a separate session of cardio for strictly fat loss, I'm keeping insulin quiet before it and a bit after it. Nobody is talking about drastically cutting your daily cals/macros/protein.