I'm the first to combat the illogical f-ardism on these boards, but exhibition matches mean jack ****.
Saying Nadal is the GOAT because of this is about as relevant as 90's Clay's diatribe about Sampras owning Federer cause he won a couple tiebreaks against him in some joke match in Macau.
It was call "battle of the surfaces" it was a translation from "la batalla de las superficies" in spanish, i saw that exo, the grass part was awfull, with a lot of bad bounces, it's a cool idea but the player thats plays from the clay part will be in advantage allways