Maybe the quote is about the critical period hypothesis[0], which is not universally accepted.

0: https://en.wikipedia.org/wiki/Critical_period_hypothesis

Well, the part that was claimed. "The brain has a narrow window for learning to speak beginning around ages 2 to 3, he explained. After age 5, the window for learning spoken language is permanently shut." The person seems to mistake the term "speech" for the phrase "language comprehension"—the field moved past that decades ago.

I was extremely confused by this statement because well... I exist. I didn't start speaking until around 5 because of various health issues and I wouldn't say I was reasonable at it until I was a preteen, but I definitely acquired language, just extremely slowly.