Yeah, this is easy to check, if you don't have a stetoscope, use a long screwdriver, just place the screwdriver on whatever you want to hear and place your ear on the end of the screwdriver, it should help you ID what sound comes from where.
Still, I would ask for the spec sheet for the pistons and bore measures that where taken from the machine shop.
If I am paying 3/4k for an engine, I want to know exactly how it was built, using what parts and what clearances where measured during the build. I want to know rods used, if the ends where measured and balanced, how much weight needed to be removed from where to balance everything.
Putting a performance engine together is not just taking parts off the shelf and scewing everything together. It takes planning and this information is critical for you to know.
Without this information, there is no way to know if what you are hearing is normal or not.
On a side note, I would never run pistons with a clearance of 0,006 for a daily driver. The constant start / stop of the engine will prevent the engine from reaching the correct expansion of the pistons and you will end up with an engine needing a rebuild quickly because the bores are going to be out of round.