I've been fighting on Brazier's side here, but i have to agree with the other poster. There is no way Brazier knew he was guaranteed through as a fastest loser from heat 1.
Guys, let's be real. The odds of 6 people running faster than 1:46.97 in 4 more heats (and those 6 people not getting top 2 in their heat) at the 1st round of the USATF championship 800m in hot weather is basically zero. He knew he was in with that time, check the history of this event.