I thought they were shipped filled and factory tested unless...

I thought they were shipped filled and factory tested unless that has changed ?
Only reason to change liquid is contamination as it was not the liquid that had a lifespan? I am not up to date as I once was and I appreciate you looking So still a mystery to me as to what "service" on site required anything to do with tank and fluid.
Changing format of where stuff was mounted may give better access from front which in pods is the only easy access .so basically pumps , pipes, sensors and computer module are key components that have a limited life and we know some pumps have required replacing. Position change to achieve that would make sense .

All guesses from my end.