The last time I tried this with Tableau Server and TDE's, the user has to specifically "refresh" the data or switch to a different workbook and then back again. Basically Tableau Server grabs a copy of the TDE file when the user opens the workbook and doesn't check to see if it's updated until required by the user.
If you are trying to explain something different, please let me know.
Thanks Chris. You have addressed it partially. My question was, when a data refresh is running in the background, will a user see any errors or slowness on dashboard interactivity?
Not that I've ever experienced, I don't use Server a lot but we do have some clients that refresh extracts multiple times per day and they never seem to have an issue.