The festival zone's level is based on the highest level of pet in your party (aside from the lowest level enemies can be being lv10, regardless of if your full team is under that)

Enemies in the other zones also get those boosts (mirroring prof point gain that the player gets, hence the levels the boosts happen at), the enemies are just locked at a static level in any given area based on the location's point in the plot progression, rather than scaling to the player's level