Your understanding is correct...
but what is odd is the need to explicitly make the resource unavailable...
if the TWS definition are correct there is no need to explicitly reserve the resource...
when TWS submits/schedules a job the resource is automatically enqueued/reserved
unless , that could be the reason for the explicit enqueue/reserve, the job is submitted outside of a TWS plan/schedule
When I tell somebody to RTFM or STFW I usually have the page open in another tab/window of my browser,
so that I am sure that the information requested can be reached with a very small effort