OK, sorry. I overlooked that you were not changing the stroke:none but the fill:none. (And I did not see any filenames, as I just copy-pasted them from your comment in WYSIWIG mode.)
But then the good result is entirely accidental, and cannot be generalized to other images that contain a 'none' filling or stroke.
I think I understand what was causing the problem, though: because this image did not have a black outline with white/blue fill, but had a black ouline without fill, and an exactly matching white/blue area without outline inside it, the latter gets white/blue pixels that are partly transparent when rendered as a raster image. Normally only the black outline touches the transparent background. Apparently the palette did not contain the white/blue with the required transparency, and rounding took place which either made the pixels entire white/blue, or entirely transparent. (Mostly the latter, it seems from the mottled result.) When you apply the fill to the outline, the holes in the inside area make this fill shine through, which camouflages them. In fact these stroke:none elements seem entirely redundant if the other elements are filled.
This SVG was probably generated automatically with the help of an edge-tracing function; these often do not treat the outlines as outlines, but as borderless black-filled areas, tracing both the inner and the outer side of the black lines. And then they create separate areas for the interior.
OK, sorry. I overlooked that you were not changing the stroke:none but the fill:none. (And I did not see any filenames, as I just copy-pasted them from your comment in WYSIWIG mode.)
But then the good result is entirely accidental, and cannot be generalized to other images that contain a 'none' filling or stroke.
I think I understand what was causing the problem, though: because this image did not have a black outline with white/blue fill, but had a black ouline without fill, and an exactly matching white/blue area without outline inside it, the latter gets white/blue pixels that are partly transparent when rendered as a raster image. Normally only the black outline touches the transparent background. Apparently the palette did not contain the white/blue with the required transparency, and rounding took place which either made the pixels entire white/blue, or entirely transparent. (Mostly the latter, it seems from the mottled result.) When you apply the fill to the outline, the holes in the inside area make this fill shine through, which camouflages them. In fact these stroke:none elements seem entirely redundant if the other elements are filled.
This SVG was probably generated automatically with the help of an edge-tracing function; these often do not treat the outlines as outlines, but as borderless black-filled areas, tracing both the inner and the outer side of the black lines. And then they create separate areas for the interior.