Github user HyukjinKwon commented on the issue:

    https://github.com/apache/spark/pull/18664
  
    The baseline should be (as said above): Internal optimisation should not 
introduce any behaviour change, and we are discouraged to change the previous 
behaviour unless it has bugs in general.
    
    So, the issue is the previous behaviour without-Arrow does not respect 
`SESSION_LOCAL_TIMEZONE` but we should respect; however, this is a behaviour 
change so we should discuss further and possibly introduce a configuration to 
control this to prevent the behaviour change. Also, to be clear, I assume we 
admit not respecting `SESSION_LOCAL_TIMEZONE` is not a bug but a behaviour 
change to be fixed as an improvement, right?
    
    How about matching the behaviour with-Arrow to the previous behaviour 
without-Arrow (not respecting `SESSION_LOCAL_TIMEZONE`) first and then 
separately make a PR to introduce a configuration to respect 
`SESSION_LOCAL_TIMEZONE` for both?
    
    
    
    I actually think I a little bit doubt about respecting 
`SESSION_LOCAL_TIMEZONE` when we `collect()` or `toPandas()`, and want to 
separate this discussion into another PR, JIRA or mailing list if possible.


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