CEO of Bolt here. Browser autofill is a very detectable pattern, amongst hundreds of other patterns that all become elements of a broader fraud model. This broader fraud model doesn't only incorporate behavioral features, but literally hundreds of other features around order details, personal details, shipping info.
May smell like BS (a lot of companies in this space are full of BS). But, we spent 3 years building a world-class data ingestion & ML engine which we'll describe more in future blog posts. And our case studies (https://bolt.com/case-studies) with more to come demonstrate the type of results we're able to achieve.