I'm not playing down the importance of the blade, or saying that the blade is not (part of) the keris. And I'm also not disrespecting the skills of the smith/empu who made the blade. Don't go to the other extreme.
Yes, the "blade is the sword", but what kind of sword?
Take me for example. I'm ethnically Chinese. Both my grandfathers came from China. But I'm not going to dress like a China Chinese and tell people that I am a Chinese National. Genetically, I'm the exactly the same as the people from China, much like Taming Sari was forged by a Javanese empu. But I'll tell you my identity is a Singaporean of Chinese descent, here in Southeast Asia, part of the Malay world.
So what happens to a keris that makes its way from Java to Peninsula Malaysia? Yes, the blade was made by a Javanese smith. But now that it has made its way to the Malay world, and dressed as such, is it still a Javanese keris? Would any Americans of German descent say that they are Germans? I think they call themselves Americans.
Take another example. The firanggi swords used by Indians. Blade may be European, but I'm sure you won't call it a European sabre/sword in its present dress. What about Ethiopian shotels?