The five step method says:
a. FIRST RULE OF BRAKING: ALWAYS BRAKE IN A STRAIGHT LINE.
b. Never brake while turning. "
This is true for the novice, EXCEPT in accident avoidance. The first thing they teach you at the BMW Performance Center is a panic stop in a turn. I can't believe he writes it as an absolute, but I guess he's writing for novices.
For track driving, there's "trail braking". You're not ready for that yet, but if you stay serious about AX and track driving you'll learn it soon enough.