It's pretty hard to turn down "free" flying of any sort let alone multi time, when you're a 200 hour unemployed hour builder. And picking up empty sectors and positioning flights in an IFR twin is awesome experience. Even 50 or 100 hours of that stuff will really make your CV stand out at certain regionals who still value that kind of old-skool hour building.
However, small GA piston-twin charter operations the world over, are renowned for taking the piss out of their so called "employees" because they know fine well we're all desperate for the hours, we will turn a blind eye to a lot of stuff that maybe we shouldn't, and we will bail out at the drop of a hat / sniff of a real job and another muggins will come get the "free" flying.
You should really be 100% clear in your mind whether any laws are being broken, either employment laws or air-transport laws, if they are then it's probably not a smart move to get involved in it.