Is it possible to explain the below and why it is not supported by PCF?
Admin Processes
Run admin/management tasks as one-off processes. This is not currently supported by PCF, so applications and application suites that require this functionality need to be examined more closely for replatforming suitability.
You may want to look at running tasks on Cloudfoundry: https://docs.cloudfoundry.org/devguide/using-tasks.html
So yes, this is supported.