That option is a little confusing. By default the driver will wait for vertical retrace before doing a DRIVER based flip of the background to foreground buffer. By setting:
Option "ALL/1/General/tearfb" "0"
You will allow the driver to flip whenever commanded. Unfortunately the driver is NOT in control of every page flip. Without looking at the code, my guess is the program itself is directly commanding an immediate page flip (OGL can do that) and that is cauing the tearing. You would need to add a sync to the vertical refresh to the code itself to correct that issue.
Since it is just a demo, I would not worry about it too much as this sort of progam *GLXGears is another "bad" program) is not a very realistic use case.
Hope this helps.