I had the same problem trying to work with the table. I ended up changing the expression from just the name of my column:
to cast it to the same date format that you would get by using the number tab like follows:
=DATE([timestamp_disposition],'M/D/YYYY h:mm:ss[.fff] TT')
Per Daniel's advice you can do that formatting for your columns ahead of time by making them Measures and then use the Measure in the table/chart instead of the column itself to get around the issue.