In the Advance SVG Export dialog, when I edit the filename to be different than the default file that already exists and then clear the checkbox for "Overwrite existing file without asking" just to make sure that I haven't already created a file with the modified name as well, then I get a popup warning that the export would overwrite the default filename, not the name as edited. In other words, the overwrite check ignored the fact that I edited the filename.

Observed on MacOS Mojave (10.14), but probably applies to all.