That would seem pretty normal to me as much as 20-30 years ago. I know I originally thought of the comic and TV shows as “Snoopy” or at least “Charlie Brown.” Learning the actual comic was named “Peanuts” seemed more like a trivia thing. It’s similar when you learn a song you know by the first line or chorus is actually called something else never mentioned in the song.
“Peanuts” is just not very unique like the other “titles” that people have given it themselves over the years. I’d be tempted to write “Peanuts (Snoopy)” when referring to it, per the above.
Yeah, as mentioned earlier, Schulz himself didn’t like the title “Peanuts,” and avoided using it whenever possible.
Almost none of the TV specials, which is where young people today are most likely to encounter the characters, had the word “Peanuts” in their titles. Instead, they tended to be called Something Something, Charlie Brown or A Charlie Brown Something Something.