He doesn't take it too seriously, I doubt it can do too much harm. Just use it for a bit of match practice, and it means he can cut his number of practice sessions to 142 a day instead of the usual 143
Perhaps - I just think he has very limited time he can be on a match court on hard surfaces and be competitive without picking up or exacerbating injuries. Common sense would suggest he stick to singles when not on clay therefore.
I don't think Nadal steps on a match court to have fun regardless of the type of contest he's in
But hopefully he'll emerge unscathed.