Isn't inkscape's native data format SVG?
https://inkscape.org/en/develop/about-svg/
> The Inkscape project does not only use SVG as its native file format, it also takes part in the further development and refinement of SVG features by delegating a representative to the W3C SVG Working Group.
It's more of just their personal classification of the software than anything in my reading.
That said, Inkscape can default to save in SVG, can actively contribute to the SVG standard, but still be / come across as primarily a vector image editor.