US manning requirements, not European ones. Those feeders run with a skeleton crew, often spend less than 5 hours on a dock, and hit ports very close together with tons of river, canal, and lock evolutions.
Every time I look up the dock in Germany and see one with 5 degrees of list while being loaded I imagine that everyone onboard is trying to steal a couple hours of sleep versus tending to ballast or the mooring lines. I just don’t see how they can remain STCW rest hour compliant and generally try to stay far away from any feeder I encounter.