Of course it isn't. It shows that the only surface Nadal is actually consistent on, is clay. Other than that its pretty much in the air( except to an extent grass but then the season isn't long and Nadal hasn't defended any of his titles there despite liking the surface).
Consistency doesn't have anything to do with DEFENDING titles, but winning as much as possible on said surface, or even reaching latter stages.
If Nadal won only in odd years certain smaller HC events(and thus defending none of them), he would have a buttload of HC titles yet NO HC DEFENSE.
If Rafa entered tournies with mickey mouse draws like Bangkok/Tokio each year, without exception, and defended them 3-4-5 years straight without pause(while failing to win MS/GS against the top HC guys), would that add credence to his HC cred?
I seriously doubt it.
If they wanted to show Rafa's propensity towards one surface, they should have pointed out nr. of HC TITLES, not how many title HC defenses he failed.
Out of 60 titles, 14 have come on non-clay surfaces. So 14 possible titles defenses. But even that number gets lower if we look at the facts(the situations where Nadal was actually back next year to defend):
2005:
Madrid Masters - won it. Failed to do so in 2006 by losing in QF.
One
Canada- won it. Failed to do so in 2006 by losing in 3R.
Two
China Open - won it. Didn't enter next year so he couldn't defend.
2006:
Dubai - won it. Failed to do in 2007 by losing in QF.
Three
2007:
IW - won it. Failed to defend it in 2008.
Four
2008:
Canada - won it. Failed to do so in 2009.
Five
Olympics - won it. We'll see if he "defends" it in 2012.
WB - won it. Couldn't come back next year due to injury.
Queens -won. Couldn't come back next year due to injury.
2009:
AO - won it. Lost in QF to Andy in 2010.
Six.
2010:
WB-won it. Lost in F in 2011.
Seven
USO and Tokio- we'll see if he defends them.
In six years at the top, Rafa had only SEVEN opportunities(6 HC, 1 grass) to actually come and defend his non-clay titles. That says a lot. Not to mention the level of competition, with the exception of Dubai, the rest were HC MS(and there are MANY guys better than Rafa on HC) or GS(WB 2011 failed defense).
It's kinda funny that a guy like Rafa, who wins 1-2 non clay titles per year, gets berated for not defending(exactly those) next year.
A guy like Murray, with far more HC ability, playing on his fav surface 60% of the time, has defended a HC title 2 TIMES(if his wiki page is right): Canada 2009-2010 and San Jose 2006-2007.Djoko defended on HC 3 TIMES(Dubai twice, Beijing once).