Permission issue when connecting to printer - Unable to open serial port, operation not permitted

You cannot compare the two. In Klipper, the host process running on the SBC (or in your case in Docker) is the central “brain” of this solution and is responsible for maintaining the necessary timings and it requires constant, precisely timed and permanent access to the MCU. Any delay or interference will result in Klipper errors.

For a better understanding of the Klipper architecture refer to Klipper Architecture / Ecosystem