Don, I looked at all of my other pistons under the microscope. The ones from the problem motor are down south. You are right. The grooves are not machining marks and it looks like they are deliberately put there as part of the surface finish.
Konkretekid sent me a link to some literature on piston alloys. The low-silicon 2000 series alloys in these racing pistons are especially strong and well suited to turbo and fuel use. In comparison to the 4000 series high silicon content alloy pistons, they do not wear as well and they are set up with a little more clearance.
The Arias piston to wall clearances are tightest for race motors, a little bit looser for the street, and they are looser for water cooled engines as opposed to air cooled motors. This is the opposite of what we did in the old days. This new stuff is definitely different.
Deck heights can be measured when the engine is put together. I like to measure everything up before assembly and calculate the deck height by math. It is easier. The new and old engines use the same crank and crankcases. This makes the job much easier. The standard OEM engine deck height was OK and it is my point of reference.
First, I bring everything I will measure to a room with temperature as close as I can get to 68 degrees. This house is heated with wood and the rooms all have different temps. The kitchen is closest to ideal. All of the measuring tools are included. Everything should be close to the same temp for measuring. The items sit around for an hour so the tools and parts will be the same temp as the room. That is why I am typing this post. I am waiting.
Some parts are hard to measure because they are bigger than my micrometers. The cylinders sit on a flat metal plate and a dial indicator is used to get a height reading. I use my drill press table for the plate. I measure the standard cylinders once, then the new ones, then the new ones again, then the standard ones. The first and fourth readings should be the same and the second and third should be similar to each other. This is ABBA measuring.