As not having heard about this before, my initial thoughts is why Grumman would take notice of the German lightweighting when they obviously didn't do it around the primary opponent to the Grummans: The Zero?!
Grummans response to the dominance of the Zero was a bigger engine into a similar airframe wich finally became 55% heavier. Though lightweighting isn't the major quality of the traditional american industry, it seems straightforward to try minimize the weight on the upcoming design after the F6F - Even without the presence of the Butcher Bird.
Just my 0.05$