Investigation has shown that the Absolute Pointer Protocol (APP) is not available during startup, even with the Dell BIOS upgraded to revision A10.

You can determine if the APP is available with the UEFI-based tablet test tool (for details, see KB78050). During a normal boot sequence, during testing, the UEFI-based tablet test tool does not allow you to use the touch input. But, after starting your computer and enabling the One Time Boot menu option, the APP becomes available and the tablet test tool tests are successful.