The pistons may actually be installed "correctly". The arrow pointing "front" does appear to be pointing to the front of the engine, if that's the engine stand I see on the right side of the pic.
Someone modified those L2355 "six pack" pistons by milling a dish in them...they are normally a 4 valve relief design. I've never seen a dish like that on the "top" side of the piston before, that would ruin any quench you may have had. It's possible whoever machined the pistons put the dish on the wrong side of 4 of them.
It really won't hurt anything, just not the normal way of doing it.