Can it actually predict Marketplace tech-review failures?

About 80% of them, yes — the deterministic ones. Things it catches reliably: vendor edits, raw SQL, deprecated APIs (anything in @deprecated blocks across vendor/magento/*), missing service contracts, hardcoded URLs, missing translations on user-facing strings, missing composer.json dependencies, license file mismatches. Things it can't predict: subjective UX issues, regional compliance flags (GDPR, ADA), and Marketplace-listing copy. For those you still need a human reviewer (hire one). But shipping a PR with zero deterministic findings means the human review is fast and pleasant instead of soul-crushing.