I'd expect even a midwit like Mike would know if clickloc or not...
my best "guess" is cold material that spent a high desert winter night or three in the van and pulled right from the van to the floor.
and/or possibly a cold weather install before the HVAC was operable/running in a rush to complete a rehab
(been there/done that..."once" )
Installed over uncured concrete is possible too, but think that less likely
..L.T.A.
Larry, You are onto something about the uncured concrete.
I recently had a flood in my bathroom. The leak traveled under the tile and into my walk-in closet. I thought I had a leak in the closet under the slab, so I ripped out all the carpet in the closet. Once the leak was fixed my wife wanted hardwood in the closet. Ok, so I've dried everything in the closet, ordered some flooring, then placed it loosely in the closet so it could acclimate while I was gone on my Mexico adventure.
Last night I was working in the closet pulling the base boards and tac strip, when I picked up one of the boards off the floor it had some green mold on the back. It looked like it has soaked up some remaining moisture from the slab, even though I thought it was dry. apparently it wasn't as dry as I thought.
I'm glad I discovered this now and not before putting down the wood flooring. I'll be gluing it down because I'm not a fan of floating floors. I installed a heater in the closet and might also put a dehu in there for a few days. I'll Seal the concrete floor with a moisture coating, then start the process of gluing in the flooring.
The moisture moving through concrete is a real thing. It's susceptible to capillary pull and hydrostatic pressure. If I didn't let that wood plank sit there for a week, I would have never known. The feel and look says dry. The board says different.
Also, the OP shows flooring that was glued down but Mikey says it's floating click lock. I would read the instructions. Many click lock floors also state they can be glued down. That is what I'm doing in my closet. It has the option for both. Glue is a better option in my mind. I don't like how floating floors sound or move around. All the lippage in that pic looks like someone mopped it and the floor isn't water proof. Not saying that is it, but it looks to me that way. Also many say water resistant, but it's just the thin top layer. The edges and bottom are not.