I use Arches Platine paper for my Pd/pt prints for more than ten years now.
Most of the time I use pot.oxalate as developer for 2 minutes and it's enough. Not less but longer will not really help.
Just two things to get it cleared after that: the first water bath MUST be on the acidic side.
To be sure of that I always put one tea spoon of citric acid in a liter of water. Two baths for one minute (1/2 liter each time).
Arches Platine must be cleared after that with a working solution of HCA from Kodak or it's equivalent Sodium Sulfite 20g/liter. 2x 5 minutes.
Wash for 15 minutes and your print will be cleared.