Other mistake: When Oliver is meeting Fagin and his boys, he says, "Is this a laundry then, sir?" You can see Jack Wild (Dodger) mouthing that line on the left side of the screen.
Other mistake: At Fagin's place, Bill is supposed to give Nancy a back-handed slap that sends her to the floor, but there's no sound of the slap and there's no contact - it's very badly acted.
Chosen answer: You are correct that "Oliver" does have some material that might be intense for young children - including a murder, some minor violence, issues of adoption, child abuse, kidnapping, and even some sexual content (but only by innuendo). Drinking alcohol is also involved, and some of the characters with whom we are meant to sympathize are, in fact, thieves. But intense content does not necessarily preclude a movie from obtaining a "G" rating. There have been several G-rated movies which have content, including killing, that could be frightening for children, including "Bambi," "The Lion King," "Willie Wonka and the Chocolate Factory," and "The Wizard of Oz," to name a few. In "Oliver," most of the violence is alluded to, and the murder of Nancy is committed out of sight (only Sykes' hand is visible, and Nancy's screams are heard), though it is frightening and realistic. Violence can be permitted in G-rated films, as long as it is "minimal." Sexual innuendo is permitted, in small doses, as long as lewd acts aren't shown. Intense content is also permitted. Drug use is not permitted, but I suppose the tavern scenes are cartoonish enough as to not warrant a more harsh rating. The bottom line is that ratings are determined by the MPAA - Motion Picture Association of America, and that association is given wide latitude and discretion. Apparently, the "mature" content of "Oliver!" was not viewed as rising to a level which the MPAA felt would warrant a more stringent rating.
Michael Albert