Created attachment 175515 [details] shapes with ooxml gradient attribute path="shape" ODF has the attribute draw:concentric-gradient-fill-allowed (19.124 in part 3 of ODF 1.3) for the <draw:enhanced-geometry> element. That attribute is not implemented in LibreOffice. That element would allow that a gradient starts at the edge of the shape instead of the bounding box. Having it implemented in LibreOffice would allow a better import of the ooxml child element <a:path> of the <a:gradFill> element for the case it has the attribute path="shape". I have attached a pptx file which has shapes that uses this attribute. In addition it has images of how it is rendered in PowerPoint, so that you can compare it with LibreOffice.
The standard ODF has yet no details about it, see issue OFFICE-1866 (see URL). So when such feature is going to be implemented, it has to be done in close contact to the ODF TC.