“So - given I will not be traveling with full tanks (only what is potentially used during travel from campsite to campsite”
You are assuming the campground water is working when you arrive. What if it isn’t? You are willing to pass up the beautiful dry campsite you spotted from the road? No water in your tanks. Lots of those CGs out West. Running at or close to max for your tow vehicle and/or the trailer isn’t fun.
What if you don’t like the taste or smell of the campground water? Tuff, you must fill up.