Do both LP tanks pull simultaneously?

I am confused I thought that LP only pulled from one tank and then when it ran out the regulator would automatically switch to the second tank? I noticed with Mopeka sensors that both tanks are pulling simultaneously. See my image…

I filled Passenger Side tank last night 100%. I turned it on and when I checked this morning both tanks have dropped in level overnight. It leads me to believe the regulator is pulling from both tanks simultaneously.

I dont know anything about the Mopeka sensors or how they measure, i do know that the on-hose-or-fitting analog indicators are never very accurate. Temperature makes a huge difference on pressure in tank, if it is quite cold you dont get as much out of your tank as if it is warm - i am stationary in north east so i use 100Lb tanks on my z3100, and if mine switched over night i often switch back and forth to see if i can get a tad more out after it warmed up during the day.

it should only pull from the primary side (my regulator is a kind with the white cover on it, pretty sure it is a flame king or derivative/oem of the same, the long end of the black selector knob is the pointer, not the other way around which naturally would have made more sense to me with a long end tail and an arrow on the knob). On a different rv in the past i once replaced the orginal regulator/switcher with a flame king (https://www.amazon.com/gp/product/B08XYH1JS7/), looks the same as what my z3100 goes, the reason i replaced it is the old one had an indicator which seemed to stop working when it got below 15 degrees F, so i didnt trust it - the flame king had lots of good reviews.

perhaps check a couple nights in a row and see if it continue to drop or if that is a standard morning reading at a certain temp. never know if there could be a leak also - either way if you call RV consumer support they are really good at trying to help you, open a support case etc. (i used them for a furnace issue that got fixed)

I had the mopeka sensors on my last trailer and they can be a bit inaccurate. The system only pulls from one side at a time.