While he's technically the same character, the mood and setting are definitely distinct in the two projects. On Mindhunter, Herriman portrays Manson in jail during the '80s, a stark contrast to Tarantino's colorfully nostalgic Hollywood in 1969. His reprisal of this role was purely coincidental. In fact, he shot and completed his performance for Mindhunter before Tarantino's announcement of the movie's cast. Despite this apparent conflict of interest, Tarantino gave him the stamp of approval to be the character in the movie.
Of course, Herriman isn't just the guy who plays Manson.