Does that mean Telemundo and Univision are poor quality?

HYPOTHESIS: Telemundo and Univision are watched by a lot of recent immigrants from Mexico and elsewhere in Latin America. The reason they immigrated was because in their countries of origin they didn't have a lot of opportunities including education. However their children, who are more likely to go to college, are also more likely to have news sources that are not Telemundo and Univision. END HYPOTHESIS.

Is the similarity in graduation rates recent or decades old? As a fraction of adults 25 and older there appears to be a wide margin of about 30% vs 11%.

Not necessarily. The kids of Hispanic immigrants would naturally speak English far more commonly than their parents thus they'd have more choices for their news. I hear Univision is starting to get more conservative lately though so that might have an impact on the viewership statistics.