Those are just the jazz holdings. They also own tons and tons of other imprints in other genres.
(Other EMI jazz labels off the top of my head: Liberty, Jubilee, United Artists, Solid State, Aladdin, Jazz West. I thought they also owned Elektra Musician but Wikipedia suggests it's a Warner holding. Maybe they only got part of the EM catalog like the Bird and Diz Washington concerts?)
Pretty sure it's Warner's. Elektra is the "E" in WEA.