
The FNAF 3 training tapes disprove BVPostMCI
Most of the counter-arguments made by BVPostMCI believers hinge on the idea that the "1985" date given in the books and movies does not necessarily translate to the games, and that the MCI can still take place before the Bite of 83. But there is information inside the games only that can prove that the MCI takes place after the death of the Bite Victim.
The training tapes played in the FNAF 3 phone calls are implied to be played in order of when they get recorded, meaning the events that are implied in them is linearly organized chronologically. Night 2 and 3 talk about how to safely use the springlock suits, but suddenly, in Night 4, the springlock suits are now unfit for use by employees, due to "an unfortunate incident at the sister location involving multiple and simultaneous springlock failures". Because we know that Fredbear was a springlock suit, this means the banning of the springlock suits must happen after the death of the Bite Victim.
Night 5 is where things get interesting. The training tape played this night is reminding all employees about appropriately using the safe rooms, and it make sure to specify that "under no circumstance should a customer ever, be taken into this room, and out of the main show area". We also get clued into the fact "that the Spring Bonnie animatronic has been noticeably moved". With the added fact that Follow Me is likely paralleling the events of the MCI, we know that this tape must be referring to the events of the MCI, and that William likely lured the kids to the safe room before killing them. Night 6 then states that the safe rooms are being sealed, further reenforcing the narrative that these tapes are in chronological order. This means that the MCI has to take place after the banning of the springlock suits, and therefore must happen after the Bite of 83.
You might try to argue that MCISpan could fix this narrative, having William kidnap the first few kids before BV dies, and then using the Spring Bonnie suit for the last ones, but this is disprovable by looking at Susie. In Fruity Maze, we see Susie being lured to the back by William, wearing the Spring Bonnie suit. And because Withered Chica/Susie says "I was the first, I have seen everything" in UCN, this shows that Susie was the first victim of the MCI, possibly the first victim of William. But with the training tapes that we've discussed, we know that she cannot have been killed before BV dies.
All in all, the training tapes from FNAF 3 paint a pretty clear timeline for these events. The springlocks are used, BV dies along with other springlock failures, the springlocks get banned, the MCI happens, and then the safe rooms get sealed. This solidifies that BVPreMCI is the correct interpretation. What do you all think?