The Principle of Contingent Causation: The Impossibility of Infinite Regress.

[GrandizerII]

Modern Science 100% confirms the Philosophical Truth established by learned Philosophers long ago. I will quote Alexander Vilenkin and then shake off the dust: "THE OBSTRUCTION may be found in the Borde-Guth-Vilenkin (BGV) theorem.8 Loosely speaking, our theorem states that if the universe is, on average, expanding, then its history cannot be indefinitely continued into the past ... No matter how small the probability of collapse, the universe could not have existed for an infinite amount of time before the onset of inflation." https://inference-review.com/article/the...e-universe

Again, the BGV theorem doesn't say that any universe must have a beginning. There is a condition to keep in mind here for the BGV to apply. The universe must, on average, be expanding.

So even if this observable universe is expanding and thus has a beginning (per the theorem), there could be a "higher-level" universe out there that exists but is not expanding and which doesn't have a beginning.

And the article you share here is Vilenkin's view on what universes are possible/plausible, not just what the BGV theorem states. So he is going beyond what the theorem itself says. Vilenkin is not the sole authority on this matter though. Alan Guth, one of the two other founders of the theorem, disagrees with Vilenkin and thinks it is possible for there to be a universe that is eternal. The BGV theorem itself doesn't make a statement about who between them is correct.