[Jens Wendorff]

But Fuel FILTERS for sure are not tested or stored wet, as there are no mechanical moving parts inside. Filters should come bone dry!!!

Can you imagine to buy a "new" filter which has been "tested" ????
If they would have tested the filter for its capability, then dirt particles would have been filtered out already-so you will no longer get a new filter but a contaminated one.

For the pumps, its a different story. They are stored wet. Maybe different suppliers use different stuff (gasoline, kerosene, petroleum, alcohol.
I once returned a broken fuel pump which quit after only 2 weeks of operation to the dealer. He sent it in to the manufacturer and the reason for failure was confirmed to be corrosion at the roller pump cells due to improper (dry) storage.
Got a new one with apologies.

Jens