What is different about metering for negatives and metering for digital is that digital ISO is determined by a resulting JPEG that comes from the standard ISO process for digital, essentially the "final result", much as for slide film.

The resultant JPEG is a result or the sensor and the manufacturers software, hence different for every camera. A DSLR can get you a reasonable exposure setting at a given ISO but it is far from being able to mimic a negative.

ISO for negative film is keyed to the negative's density at certain points. Negatives are an intermediate medium, while there is an ISO speed point film can, for example with XP2 a 400 speed film, be shot at 50,100,200,400, or 800 and create nearly equivalent prints, the "final result".