I attended undergrad in the mid-late '90s and yes, social science and humanities classes did hand out C/C- and failing grades.
Some like that classmate took far longer than normal to graduate due to being placed on academic suspension(flunking too many classes) and/or parents forcing them to take mandated gap years when they received too many C-/C grades. Knew of a few who were academically expelled as well in a wide variety of majors including humanities/social sciences.
One college classmate who was repeating an advanced Poli-sci seminar because he flunked it before was overjoyed to receive the final grade of C+ on his seminar paper as that meant he could walk and actually graduate that year.
And this wasn’t only at my college or during my time, either.
Several years after I graduated in the end of the '90s, while waiting to see a grad Prof for something I happened upon an irate undergrad at an Ivy who apparently mistook me for the US History survey course TA who awarded him a C on a term paper.
Couldn’t help reading it considering he rudely thrust the essay in question right in front of my face.
And yes, the content, analysis, and writing quality were so abysmal that I actually felt his TA was being too generous and told that idiot undergrad as much. He apparently had the benefit of an elite private NE boarding school education considering he kept mentioning it along with wearing something with his boarding school’s name.