amplify gen2 sandbox with existing stack

With command:

npx amplify generate config --app-id <id> --branch <branch> --format json --out-dir config

It correctly generate amplifyconfiguration.json file in config folders with correct IDs in it that correspond to <branch> already deployed stack.

But then with command:

npx amplify sandbox --config-out-dir ./config --format json

It don't care about whatever options I've tried and every time re-generate a complete fresh new stack with a new amplifyconfiguration.json file in project's root folder.

This is not what I want.

What I'd like is a sandbox that use backend stack from an already deployed branch (with seed data).