He essentially did become a different being when he absorbed the Daikaioushin, before that he was just mindless destruction and evil incarnate. Either way, prove he knows of Kid Buu and his strength.
The statement is inaccurate because it is contradicted within like three chapters, yes lmfao.
As you pointed out, his statement is limited by his own knowledge, now prove he knows of Kid Buu and more importantly Kid Buu's strength, since the author seems to think Buu himself doesn't even know how strong he is.