Question:

saturation level can be negative?

How to reproduce:

Give yourself an item with negative saturation:

/give @s minecraft:grass_block[food={can_always_eat:true,eat_seconds:0.05,nutrition:0,saturation:-1}] 64

Expected behavior:

Item Stack Component "saturation" can be negative
However, the saturation level cannot be lower than 0 after eating.

Or Component "saturation" cannot be negative

What actually happened:
The saturation level can become negative.