Tron in 1982 also got a PG rating. Quite controversial in my mother's circle of parenting friends. "How can Disney release a PG movie like that?" said one parent.
Worth remembering that PG in those days was a very broad rating. _Airplane_ was rated PG and includes a topless scene. Indiana Jones and the Tempke of Doom was rated PG and was pretty gory for the time. Both would get PG-13 or maybe even R ratings today.
An R rating for… displaying a female chest?
PG had plenty of that in the 80s, see Irreconcilable Differences (actually a pretty good movie)
Not saying it is proper or moral or whatever. But that will do it these days. See the auto reply bot here that explains it.