Difference in Wet and Dry Screen Height

[zoigberg]

Airmann - "The definition is that it's always wet unless it's completely dry"

I would be interested to know where your quote is from. A look at Perf section of EASA 2012 gives ..

EASA CAT.POL.A.105 (d) "For performance purposes, a damp runway, other than a grass runway, may be considered to be dry."