HaHaHa. Now that is funny.
Rotorfossil - that's the first time I've heard that as an explanation of the long grass effect (not a myth then ?) & it sounds plausible. Previous explanations I've heard centre around the work done by the downwash on the medium (water or grass) resulting in lower pressure and less reduction in inflow - also plausible. Maybe a combination of both ?
I've also read elsewhere about the altimeter in ground effect, I've never noticed it but will check next time I fly.