Keep everything all in one global state is one of the good practices in the use of Redux in the development
Who told you that?
for support and extension, it is convenient to encapsulate the state of a component inside it.
nothing prevents the state to be stored in the General store
Feel the difference between "to support and expand comfortable" and "do not interfere"?
"Nothing prevents" you to write anything - but what is the use?
the price for encapsulation, we transform the component into a black box
Yes. and it's good