What is the advantage of adding the trino integration?

Initially, Pinot did not have support for joins and nested queries. At the time, folks would use Trino/Presto with Pinot to get full sql support with power of Pinot. Pinot has since introduced support for joins and nested queries with its multi-stage engine, so that gap is no longer there

Does it still have value or specific use-cases in this state?

Pinot isn’t meant for long running queries where processing can’t happen in-memory. In such cases you can still use Pinot with these systems to power real-time use cases directly via Pinot, and also ad hoc long running use cases with Pinot + these systems on the same dataset at rest

Another scenario is where you need to join data across multiple systems e.g Pinot and Postgres