Moisture vapor travels almost vertically in a concrete slab. It will diffuse off center about the thickness of the slab. It is true the moisture will travel laterally in the blotter layer and that is why the blotter layer recommendation was omitted in April 2001.
"the blotter layer" is the main problem in the West. FYI everyone - I know of a major architect who is now being sued because of their use of it in a 2006 slab. Our instructions removed the blotter layer in 1999. I look forward to getting deposed because it is not the Architect's fault. It is the structural engineer to whom they subbed out that work. I can't wait to throw him under the bus.
Even CalGreen (the new building code) still allows for it if the slab is "designed by a structural engineer". Well ... I can't wait to see one of these engineers get sued. They are the ones who are the cause in fact for 80% of the floor failures we have had to deal with. Not the flooring sub, not the gc, not the architect, not the curing compound, not the adhesive, not the material suppler, the engineer should be blamed.
It will be interesting to see what gets decided. But, it will probably settle out of court.
When a blotter is used, and there is a hole in the vapor retarder, the moisture will impact the entire slab. Example is a 16d nail hole in a vapor retarder will allow 3 pints of water through per day. That water will travel laterally in the blotter layer to affect the entire slab.
Curing compounds and sealers are a major concern to flooring installations. It is just one more thing to fail.