In this case, it depends on how you define the word "language." I distinguish "language" from "dialect" such that two dialects of the same language are mutually comprehensible, but two languages are not. But there are a lot of shades between "comprehensible" and "incomprehensible," not least when you look at the question diachronically.
Shakespeare isn't always easy to follow for native speakers of English in 2020. Chaucer is very difficult. But I would still class Chaucer as English. I would say that the difficulty of Biblical Hebrew for Modern Hebrew speakers fluctuates between the difficulty of Shakespeare and the difficulty of Chaucer for Modern English speakers. On that analogy, I would call Biblical Hebrew and Modern Hebrew the same language.
Anyway, read the essay, decide how you want to define "language," and you have your answer.
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