In the From The Ground Up course, Coach Peter suggested a high frequency small bet strategy with BU vs BB SRP on a AK3 rainbow flop.

However, GTO suggests a 60% check, 10% small bet, 30% 1.5x pot bet strategy on this scenario. Why is there such a big difference?

Here is my understanding:
I chose a small bet on the flop and noticed that GTO will raise small pairs and some very low equity backdoor flush draws as a bluff. I feel like this almost never happens in the games I've ever been in. If the BB does not raise enough, does it mean we get to bet wider with a small size?