1. Create an SVG image which is wider than it is tall
2. Ensure it has no width or height attributes on the svg tag
3. Add it to a new slide, using ShapeCrawler
4. Load the resulting slide into PowerPoint
5. Notice that the shape is square, so the image is squished horizontally
6. Now with PowerPoint open, import that SVG manually
7. Notice that the resulting size matches the viewbox attribute, so PowerPoint inferred the size from that

More on this: If the SVG doesn't even have a viewbox attribute, PowerPoint will use 500x500 pixels. That's probably not what user wants, but at least user can SEE something.