FYI, I did fully replicate your original scenario using the steps I provided above to ascertain that it would properly work. And yes, it does work. I validated that the resultant file is completely CMYK=(0,0,0,K) content. Unless you used that non-recommended PDF/X-1a setting, the file coming out of the High Quality Print settings is not SWOP. The content is totally RGB. Why do you think that it was already SWOP?
- Dov