I can only offer this. At work, the dealer of our Holmatro Rescue tools told us something similar. He stated that a WD product was harmful to the various seals and such. The advice was spray the joints and pivot points. Then spray the lobster claws, duckbills, etc and wipe them down to leave a light coating. 12 years later the tools we kept run and look almost new.
As far as the plastics, I'm not sure if it has any benefit. I plan on coating the areas that are colored with an automotive protectant when I get one.