True... and, granted, the idea about vampires being unable to survive sunlight is not an intrinsic part of vampire lore, but an invention of the silent film Nosferatu.
And intrinsic vampire lore would be... what, exactly? Because Nosferatu is as influential a vampire movie as they come (and the 'die with sunlight' idea is only the most obvious example).
Unless you're talking about mythological vampires, which aren't quite the same thing as the bloodsuckers of Sheridan Le Fanu and Bram Stoker's books.
Well, every vampire series tweaks the rules to fit their own purposes. Buffy vampires aren't exactly the same as Anne Rice vampires, which play by different rules than Underworld vampires and Blade vampires and Being Human vampires and True Blood vampires, etc.
The "lore" has never been locked in stone. Even Le Fanu and Stoker aren't consistent with each other, or the various movie versions.
Heck, the Hammer films aren't even consistent with each other!