Allen, I would go with PPG's recommendation as it appears you have their products specified. Call their tech line and get it from the horse's mouth.
This was in the link you posted:
NOTE: DPLF must NOT be applied over DPX170 or DPX171.
....where the 171 is an etching primer. I'm not that familiar with all the PPG products, perhaps there is a different etch that is compatible.
