Risk is of an event happening or not - ex, trade being a loser. Not an amount lost.I am not sure if I agree with the book.
You should enter trades when your conditions are fulfilled. Therefore, you should not risk more ("larger bet") if you feel the trade is extraordinary. Risk should stay the same. If the reward is higher (RR ratio), even better.
But I would not increase the risk.
So based on historical testing or forward testing (actual money on the line, my preference) accounting for such things as time of day, day of week, and news releases, etc plus putting aside black swan events, risk for the most part, is the same trade after trade.