It is utterly stupid to use one statement to prove one plane is based on another.
Maybe if the Grumman team had brought a Fw back, took it apart piece by piece (which some companies did after Wright Field allowed it) then, perhaps that one statement might be appropriate.
It's like saying the F6F is based on the P-47. Same dimensions, same weight class, same power plant. P-47 prototype flew first. But oh wait, thats right, they were being designed at the same time, under seperate contracts with the Navy and Airforce.
- Jig