I don't mind that you disagree with me it won't change my views.
FYI : GPF is NOT an ISU championship.
And yes, I know what you are saying : some federations do see Nationals as the factor to send skaters to worlds while others, like Japan, consider body of work. No matter how Yuzuru would have done at GPF and Nationals, I would be surprised he would have stayed home, especially this year, when Japan is having 3 spots.
For skaters doing really well at GPF, the advantage is that Nationals is usually right after... so it's not like someone doing really well in September and going through a rough phase. Yuzuru had just won GPF when he got ill, so the federation can easily assume that without the flu, he would have been in a similar shape as GPF.
Now, I have been following the sport for a long time as well, 1988... and if 4CC is not as popular we can wonder if it is exactly because the USA used to send its B team there. I see that it's picking up in popularity since both Japan and the USA have started to send top skaters. Canada most often has sent the A team or a mix of A and B team... simple enough : Canada doesn't have as much depth ... however, this meant that we heard about 4CC more than perhaps in the USA. Is it prestigious? not yet... but does it give great points for world standings : YES.
The following is based on vague recollections of various interviews and newsclips...
Davis and White were frequently second-guessed on their decision to compete at 4CC. "Need to save energy" and such. I don't think they missed many of them during their prime.
They essentially said that they felt an obligation to support skating and that 4CC gave them a chance to highlight the sport internationally and give exposure to more fans.
I think that set a level of expectation in America that Team USA would not be composed of skaters from US Nationals who did not make the World Team.