On the face of it, soul and funk are very different. Soul is an heartfelt, emotive style invented as a secularization of the Black gospel music of the times, while funk is a percussive, high energy style where every instrument is "a drum" as James Brown had it. But soul and funk are both Black American music styles that had their heyday in the 1970s, so there's some inevitable overlap between them.
There are definitely people who are clearly on one side of the line or the other--Sam Cooke is soul, not funk, and no one would call Rick James' funky music "soul"--but plenty of artists straddled the line. No artist is more associated with funk than James Brown, but what about ballads like "Man's World"? Otis Redding was soul, but often got funky, Parliament/Funkadelic's dual name is a marker of its multiple personality as a producer of both soul and funk classics, and the Chambers Brothers, Isaac Hayes, and Earth, Wind and Fire were arguably both soul and funk at once.
Ultimately, all genres are marketing tools, and what Discog's classification tells you is that they feel confident that the target audience for Funk is substantially the same as the target audience for Soul.