Initial SQL is executed only when opening a connection to the Data Source. In Tableau Server, connections are kept open for a period of time as to not impact performance for the end user (opening a new connection can be expensive in both time & resources). This period of time is different from the cache's retention period. My guess is if you try on Tableau Server after a long time (not sure how long are connections kept open on Oracle), you'll see a new row of data written.
Curious to hear from others in the community as to how they've approached this.
Hope this helps!
My understanding is the Initial SQL to be requested just ones --
in the beginning of a user session.
The session would end up on logout,
or it is terminated after some period of user inactivity.
The default value for the latter is 30 minutes, and it is defined by the
system configuration option of Tableau Server instance:
Please tell your TS SysAdmin to lower the value
and see if it would make any difference.