2.1.1298 Part 1 Section 20.1.8.35, grpFill (Group Fill)

a.   The standard states the grpFill works in all context.

Office treats the grpFill element as noFill ("[ISO/IEC-29500-1] §20.1.8.44; noFill") when grpFill appears in a text context (that is as a descendant of defRPr ("[ISO/IEC-29500-1] §21.1.2.3.2; defRPr"), endParaRPr ("[ISO/IEC-29500-1] §21.1.2.2.3; endParaRPr"), or rPr ("[ISO/IEC-29500-1] §21.1.2.3.9; rPr").