IME of Input System Package is not working when old Input Manager is disabled

Unity Engine
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1

When I set “Project Settings-Player-Other Settings-Active Input Handling” to “Input System Package (New)”, and execute Keyboard.current.SetIMEEnabled(true), I cannot use IME input in game.
When I set “Active Input Handling” to “both” and execute Input.imeCompositionMode = IMECompositionMode.On in addition, I can, and keyboard.onIMECompositionChange works well.
Why? Is this a defined behavior?