Parallel loading of data was added in TIBCO Spotfire 11.4, but reloading of multiple data tables (Data > "Reload all data") is still done synchronously in series.
When you have several on-demand tables that you want to reload at once, it would potentially speed up the loading time significantly if that could be done in parallel, in the same way as for the initial data loading.
You may need an indication in the report whether parallel loading is possible with the relevant data.