So, if you show me you can drive a car, does that mean I should give you a job of driving a truck without first testing if you can drive a truck. Be reasonable dude. Ch
I understand your concern, but if your "sample" of driving your trucks means I'm actually doing the job of driving the truck from A to B, then you have to pay for it.
I believe what OP means is just wants to test the candidate first, So OP doesn't require to pay for the samples worked. As I said its probably just lack of communication.
From the "buyer" point of view: My recommendation is to not trust in designers who have no portfolios or previous jobs done. Other option is to give a minimal task, for a minimal price, to test them.
From the "designer" point of view: Scammers wants to pass jobs as "free samples" with the promise of an unexistent "real and good paid job", doing this they can get the whole job done by sending parts (the "free samples") to different designers. I see this a lot in 3D design.