From the context that you gave probably has the meaning that 高木 had the right answer. 高木 is probably good at this before the time this statement took place, which means that it is not surprising that he got the right answer. Hence, the definition "live up to one's reputation". So if want to say this sentence in plain English it could be: You've really got to hand it to 高木. He got the right answer again.
So for example 高木 is always the top in class:
高木又考一百分了,不愧是全班第一名。
他答對了,不愧是高木。
The first sentence tells us the name 高木 has the reputation of being 全班第一名。
The second sentence uses 高木 as the reputation.
So if we just look at the second sentence, we can infer that this isn't the first time that 高木 answered the question, and answering it correctly is no surprise.
And in very plain Chinese:果然是。