As with any situation, there are few absolutes and you are bound to get answers from people who cool and those who don't. There are people out there who get their pits to breed without cooling them. Even without cooling them, many of them will slow down once the days get shorter - no matter what you do with their enclosure temps. There are two triggers to brumation - cooling temps and decreased daylight.
Having said that, I feel there is a biological imperative to cooling. Even those North American pits that live in more temperate areas experience cool and wet winters, and warm and arid summers. Therefore they respond favorably to seasonal cooling. I have found that brumating them produces more voracious appetites during the spring and summer and more vigorous breeding behavior when they come out of brumation.
Adult healthy sayi should be brumated in a dry darkened container (or hibernaculum) at temperatures averaging in the low to mid 50’s. Water should be available. I cool my snakes for 12 weeks and have had no issues with them going full tilt boogie in the spring.
.