Even if the 4CC and European scores were inflated, the fact that they scored higher than the reigning Olympic&World Gold and Silver Medalists at the same competition speaks volume about the potential, since it would mean after similar inflation is applied, they still scored higher. Plus if 4CC and Europeans are similarly inflated, then it stands to reason they are fairly comparable to each other, making the scores between the two competitions somewhat comparable although not exactly. Let's not forget, W/P also defeat Bobrova/Soloviev at the SD during GPF even though W/P had mistakes in their SD. TES tends to be a more stable score than PCS. The fact that their strength came from TES, not PCS, is an encouraging sign because should the judges bump their PCS up at the end of the season, as they often do with new teams who show promise, that's when they can turn heads.
As for FD determines the final placement, that's simply not true. Where did you get that idea?

It's always a combination of the different phases of the competition in Figure Skating that determines the winner and the SD/SP sets you for the long, therefore, are often considered quite important even though they count for less marks. D/W won the FD at last year's World but lost the Championship title to V/M. Similarly, V/M won the FD at the 2008 World Championship, but finished 2nd overall.