The fact that the writer’s room had access to a Transformers bible will likely excite fans of other forms of Transformers media since it offers the possibility that The Last Knight will include more references to the larger history of the property.
As di Bonaventura indicated, the live-action Transformers franchise still works within its own mythology, and the other content in the property’s bible may simply be used as inspiration.
That said, although the Transformers guide exists, there’s no telling how much was used in the adaptation process of The Last Knight, or the other upcoming films within the shared universe.
But now with a fifth movie coming, there’s a lot of mythology that we’ve established as well.