I’ve made components
exported them in SVG Format (to re-edit them more properly in a vector app)
Then exported them form that app (Affinity Designer)
Reimported them into KiCAD:
I have always to magnify them by 1.333
I tried also to export them with different DPI 96-300-400 but it doesn’t change.
Not all SVGs are created or interpreted the same regarding absolute size. I always add an element with a known size, like a 10 millimeter line, so that I can figure out a scale factor for import.
EVEN WORSE: I exported just a line (nota document, but selecting a line) 10mm long. So: export as SVG.
imported that file (without any other manipulation by any other app): the imported line is bigger.
Above the original
Below the imported file after have exported it with KiCAD …
You can cross check with a third program (such as Inkscape) whether the fault is on the KiCad side or with that affinity program.
Also, SVG is in a readable text format, if you open it in a text editor, you can look at what’s in the file (I guess especially the “viewbox” is relevant).