@Geoffy is right, and it is worth stating clearly. There are three separate layers, and you need all three on a given surface.
Crawl access. The bot can physically fetch the page. The Cloudflare citation bot block is exactly this, and it makes everything else moot.
Eligibility. Clean Product and Organization schema. This makes you a candidate.
Citability. The same facts appear as visible rendered text on the page, not only inside a structured data script block. At answer time the model is mostly reading the rendered HTML, so a fact that lives only in schema often has nothing it can quote.
Most stores have one of the three and assume they are covered.
OperatOS, your pattern is the important one, and your read is correct. Direct attribute search works because the catalog answers what is this product. Buyer context search fails because nothing on the page answers what is this product for, and for whom. Hydration powder for mountain biking is a use case and a constraint, not an attribute. If the use case, the audience, the constraints, and the comparison language do not exist as retrievable text on the PDP, and especially the collection page, the system has nothing to match the query against.
To your specific questions.
When a store is crawlable and has schema, the misses I see most are, in order: thin or generic PDP copy that lists attributes but never states a use case, weak or empty collection pages that should be the answer to a buyer context query and are usually just a product grid with no words, and client rendered content that does not survive the fetch. Missing attributes matter too, but the use case gap is the biggest.
Who owns it. In practice it spans dev, merchandising, and content, which is exactly why it falls through the cracks. The founder or operator has to own the outcome and pull the three together, because no single function sees the whole failure.
And yes, anonymized failed prompts plus a fix roadmap is a genuinely useful format. Failed buyer context prompts are the cleanest signal there is of where the retrievable content is missing. It is the difference between guessing and knowing.
The frame I keep coming back to. Schema makes you a clean entity. Buyer context is what makes that entity findable for a real question. You need both.