There are no vias on the picture they sent.

Check out a photo of Terrahash Avalon clone boards....they look similar but have a few more components.
http://www.btcpedia.com/terrahash-avalon-asic-bitcoin-miner/

These are very basic "boards" shown, I'm guessing FR4 0.062" standard 2-4 layer boards.

Based on the reference designs I've seen so far I'm thinking they are just 2 layer, this isn't rocket science.

There is no pcb designer in the world that would decide to route every single one of his traces inside the board through the ground plane shown on the top surface using vias. That would mean that all smd components would have to be mounted on the backside of the board.

The only reason we route certain signals to different internal layers is to surround the signal trace with a ground plane to reduce noise, or if the physical real estate is just too tight to get a signal where it needs to go.

Someone else mentioned....as a minimum you need decoupling caps close to the power/ground inputs on any chips...as close as possible. Usually I would put them tight to the chip, within 10mm is a general rule. So they decided to put those caps on the backside? Strangest design ever.

Anyone who has worked with pcb design knows this is garbage.
This looks like what happens the first time you send off a design to a pcb house and get back a pile of unusable laughable crap.
That's what I'm guessing happened here...one of their so called engineers learning to use Eagle for the first time and made a big mistake.