Not displaying data labels if they don’t fit to pyramid layer area is the default behavior of PowerPoint (tested with Office 365 version 2103 build 13901.20312).
Aspose Slides has the similar result when converting slides to image with Aspose lib itself,
but PowerPoint renders Aspose-generated files differently and those labels appear and their layout it strange, they are not aligned to pyramid layers. PowerPoint has problems of selecting them (cannot be selected separately), presenting proper tooltips and doesn’t allow doing anything with them.
Here is the project with the test case that reproduces the problem:
project.zip (35.4 KB)
Slides, exported to jpeg with aspose-lib:
aspose.jpeg (68.6 KB)
Same presentation renders in PowerPoint like this:
powerpoint.jpeg (35.9 KB)
For us, it’s not a problem that labels appear. The problem is that they are not aligned to pyramid layers.
As far as I understand, the underlying format, at least the way Aspose and PowerPoint use it, doesn’t define exact positions for labels. Aspose lib and PowerPoint generation is slightly different but nothing hints about data labels layout strategies.
Please, adjust presentation generation to make PowerPoint render it the same way as Aspose Slides, i.e. do not show those labels, which do not fit into pyramid layer area.
Supporting label placement strategy (inside, outside, left, right, etc) will be even better, but it looks like PowerPoint doesn’t support it for pyramids.