I agree, you have leak.
You can't always trust the household water meters to show a leak. I had an improperly repaired main line leak (meter to house) in a 1-1/2" PVC line. Sometimes the blue triangle low flow indicator would spin and other times it would show no movement. Even when I would throw the 1/4 turn main shutoff to the house and isolate the line, the indicator would not always show a leak. But, the area the the line ran through was just an open patch of dirt and rocks. The soil there was always a little more moist looking than the surrounding area especially if you dug down just an inch or two. Basically then entire area was saturated clay soil and so the leak depended a bit on how much water would evaporate. My water bills were sporadic as well ... sometimes they looked normal and other times there would be an anomalous few extra CCF's of use.
Point is, you can't "think" your way to a solution on this ... grab shovel and dig. Sometimes medical imaging tells a doctor nothing but, when they open up the patient and explore, they find all kinds of problems ... You have the warning sign, aka, a wet patch of dirt, now it's time to go exploring. If you're landscaper/pool guys won't do it for you, then do it yourself. There's no harm in digging around.
