ST did not mention the fire in his first statement.
From what I heard of Brendan's first interview, he talks about a bonfire they were supposed to have on the Thursday but it got cancelled. I didn't hear about a bonfire on Halloween (if someone else hears it in rest of that interview, please correct me, I couldn't listen to it all and anything after this night from Brendan I believe is tainted and finding what is truth and fiction is hard IMO)
Blaine... no fire in his first statement.
Bobby... I dunno
Barb.... I dunno
SA.... he mentions burning brush and tires sometime before TH was there, the week before or something like that.
It isn't until later in the investigation that they all recall this bonfire. I'm not saying there wasn't one, but if there was, there was nothing remarkable about it, it didn't smell (body or tires), it didn't have 12 foot flames.
IMO people's memories are better closer to the event, not weeks or months later. A bonfire may not have been out of the ordinary, if LE suggested that the fire MUST have been that night... I could see some of them changing and going oh yeah, that must have been that night. Shoot, they got BD to admit to a brutal rape and murder, getting them to "remember" a fire that night must have been a breeze.