That the ASC makes no mention of Baddon is not surprising as the policy was clearly not to mention their defeats. A further example of this are the battles mentioned in the AC and also referred to in the ByT, dated to the year 721:
And the battle of Heilin, with Rhodri Molwynog, took place in Cornwall; and the action of Garthmaelog, and the fight of Pencoed in South Wales. And in those three battles the Britons were victorious.
Moreover, although the ASC is reasonably accurate, it is clear that in the Arthurian age the information has been manipulated. The entries for the years 495 and 508 look similar to those of 514 and 527 respectively, seperated by 19 years, the Metonic cycle. It would appear that, by the use of repetition, the chronicle blanked out a disastrous period for the Saxons.