thats because if you put your file into a svg converter , you'll have a light version
but that light version is lost when you put it back into inkscape
because if you edit your file on inkscape, it adds a bunch of unnecessary lines of code with it, things like nametags and such. its really a pain. since you don't want Inkscape to add unnecessary weight to your file, you want to load the svg that you downloaded from the svg editor(preferrably this one:
https://jakearchibald.github.io/svgomg/). Make sure to not edit the file in inkscape before you upload it to warzone. I know this because I've had the same problem