2) I have seen flow tools that show the entire AS path. Are they just cherry picking which platforms they showcase for the best marketing, or are they enriching the data they receive from "lesser" platforms from an outside source?
Full AS-path information isn’t typically included in flow telemetry records. One typically receives origin-AS and destination-AS from exporting devices, along with BGP next-hop information.
Tools which provide the detailed type of information you’re describing typically provide combinatorial analysis of both flow telemetry received from edge routers and either live or offline BGP routing information.
[Full disclosure: I work for a vendor of such tools.]
--------------------------------------------