Yes, Arroyo is entirely based on DataFusion, but ArkFlow is not exactly. In the future, ArkFlow will establish a plug-in ecosystem, allowing anyone to process data through plug-ins, not limited to DataFusion.
A contrast between Arroyo and systems like Benthos and from what I can tell ArkFlow, is that Arroyo is a "stateful" stream processing engine, which means that we can support things like windows, aggregates, and joins, with exactly-once semantics and fault tolerance, at the cost of significant additional complexity[1].
[0] https://www.synnada.ai/ [1] https://www.arroyo.dev/blog/stateful-stream-processing