My guess is that they're using FastText for semantic search, so it's more likely to break queries like "coffee near me" than address search, the latter likely being handled by tantivy. For context, I've also written a geocoder [0] based on tantivy. :)
Wow Airmail looks awesome. Have you ever benchmarked it on latency? I'm working on geocoding solutions for AI agents so quick tool calls is really important.
[0] https://github.com/ellenhp/airmail