There was never an FCC requirement or specification regarding live vs. automated. That was a station choice, usually based on cost and the availability of talent.
Most of us had 5 to 6 hours of Public Affairs/Educational/Other commitments and ran either through as late as noon on Sunday or both Sunday morning and Sunday night.
Generally, in that era an AM needed 8% non-entertainment programming and an FM needed 6% to get an easier renewal. Those percentages were made up of news, public affairs, educational and some religious programs.
Typically, a music FM that did not want news in most dayparts would do heavy news overnights, and then do newscasts just in AM drive the rest of the day. Then you'd need about 5 to 6 hours of those Sunday shows to complete the quota.