Okay, I think you nailed it!
One way to avoid mucking around with post-processing the SVG is to click the More button on the Export pane. Set “Use DPI” to 96 instead of document resolution, unset “Set viewBox”, and while we’re in here might as well set “Export text as curves”. Click Manage Presets to add a preset, name it Glowforge, and use that from then on. The result is no viewBox parameter is set on the root node and the width/height is set in pixels at 96 DPI. Result imports at the right size.