Rendering is for editing and playback. It is not required for export.
I often delete all render files before exporting because occasionally, corrupted render files can cause incorrect export.
Not 100% sure I agree.
I have switched off Background Rendering for my most recent projects (1080p CK with some minor Motion transforms), the Export (to Media files) was clearly being rendered (in the activity windows/Command-9) prior to FCPX handing it to Compressor.
Are we talking about the same thing?