Why not? Is yet there yet again one rule for him and another for other players? Also if Nadal has nothing to hide then he should be willing to undergo such an examination. At least it might have the effect of putting an end to all the negative speculation about what's been going on over the past few months.
Because it would then essentially get very tricky for ATP. Then there's the lawsuit factor so unless they have something in the procedure or at least develop one (I do see some players protesting it as if there’s no tomorrow – Nadal in particular) I don't see things changing a bit. Even their drug testing model is below standard so there’s not much hope. They can’t even implement their rules properly let alone call on it.