Having had a look at your pics, here follows my not so pro opinion.

That looks like a pretty kak oil pump...kak means sh!t, but worse...

No seriously, the last pic shows some rust on the mating surface, and it might be that some of this got into the pump. The shaft might also be rusted where it goes through the housing, which is causing the tough turning.

Maybe this pump simply didn't get enough lube/wax when it was assembled, and rusted while in transit or on the shelf???