>>23662365no she couldnt have because she wasn't born yet at the point azumanga takes place. but I get what you mean so yeah ok in that sense yeah its kinda the same story BUT osaka is an adult and has a job as a teacher in yotsuba& (she only appeared in it this year, for 22 years she wasn't in it) it wouldnt have made any sense for yotsuba to appear in azumanga.
also the author started writing yotsuba& after he had finished azumanga.