is this normal for AI?

Food is a civilization level number rather than a planet one, so that world is feeding the rest of the empire and not just its own twelve citizens. A large figure on one fertile planet is not wrong by itself.

Twenty agricultural districts is. The AI weighs each tile by what that tile is best at, so on a very fertile world almost everything scores as farmland, and it does not pull back once the surplus is already enormous. That planet should have been turned toward manufacturing or research well before it reached 623.

Worth a bug report against the colony build logic rather than against food.

Illauna and I created two mods that provide two improvements that uses that excess food for wealth creation and global growth: Illauna-FarmersMarket and UP_GA_IrrigationNetwork which can be found in the bundle of mods on the mod website. It makes all that excess food quite useful. 

I used that mod and deleted it when AI made so much food they created like 100k money per turn with empire vassal, its should be something look cause making 700 food per turn is useless and this mod make food just too OP that you don't need to make tourism or money discrits 

That's sadly a problem with the latest DLCs then. The mods are way older then the DLC, years older in fact hehe.