It appears to be a typo but there isn't anything like that mentioned in an errata. Also there were two erratas for the monster manual the only entry related to the black dragon is as follows below:
p. 63 Black dragon advancement should read:
Advancement: Wyrmling 5-6 HD (Small); very young 8-9 HD (Small); young 11-12 HD (Medium-size); juvenile
14-15 HD (Medium-size); young adult 17-18 HD (Large); adult 20-21 HD (Large); mature adult 23-24 HD
(Huge); old 26-27 HD (Huge); very old 29-30 HD (Huge); ancient 32-33 HD (Huge); wyrm 35-36 HD
(Gargantuan); great wyrm 38+ HD (Gargantuan)
Therefore there aren't any official changes about this subject, although as my personal suggestion you should use the entry on www.d20srd.org, it is as close to official as you can get and it incorporates all erratas and updates to the core system.