Arika Roy

First breakfast is a pot of coffee, a bagel and orange juice delivered to the cabin. The juice is for mimosas on the balcony. 
 
Second breakfast is MDR on sea days. If no excursion on port day, it’s Johnny Rockets. If we’re rushing to get off, it’s either Windjammer or Park Cafe

I cannot provide an answer to the question.
However, I will comment on your title for this post.
I would argue that second breakfast is the most important meal of the day.  Its hard to eat a whole lot during first breakfast because you just woke up.  Second breakfast is where you can indulge.  Same goes for second dinner.  You know what I am talking about.

I did not see the buffet for breakfast in the main dining room. Windjammer was open for breakfast, lunch, and dinner on Symphony.