Amazon does indeed send an email to some owners of a product when a question about that product is posted.
This article mentions that Jeff Bezos (CEO of Amazon) wrote the following in a letter to shareholders:
From a product page, customers can ask any question related to the product. [...] We then route these questions to owners of the product.
The article also mentions the Subject line those emails will contain, as well as how often product owners can expect to receive such emails:
In addition, Amazon also emails owners - Email questions come from "Amazon Answers" (email@example.com) with the subject line, "(First Name): Can you answer this question about (product)?"
It says it will send customer questions "no more than once every two weeks, and probably much less often."
There is also an Amazon discussion thread in which people mention having received these emails.
In addition, I posted a question about a product a couple days ago and did not receive an answer, and Amazon sent me an email saying they sent my question to people who bought the product as well as people selling the product:
We sent your question about [product] to other customers who bought the product and sellers of the product, and unfortunately none of them have yet responded.
Based on what I have seen, Amazon doesn't just email people who have bought the product from Amazon and people selling the product on Amazon. Amazon probably also emails people who didn't buy the product from Amazon but did submit a product review on Amazon. This is because I posted a question about a certain product and within less than 12 hours I received answers from 2 people who I noticed had written reviews about the product, and each of those product reviews did not say "Verified Purchase" next to it, meaning they did not buy the product from Amazon.