I would say that in this case "pessimism" is a strange word choice meant more to get the reader's attention than to accurately describe what is just having a reasonable and balanced view based on the information before you. One could similarly argue for "cautious optimism" and come up with something that ends up sounding more or less the same.

When it comes to matters of optimism, pessimism and so on, I lean more on the virtue ethics angle, in that a balanced approach is what's most logical - you have to be able to see both positive and negative possibilities and realities to come to a realistic outlook. (That said, I find that in application, people who label themselves "realists" are usually closet pessimists, so I don't use that term).