Telefunc is about replacing generic endpoints (RESTful/GraphQL APIs) with tailored endpoints (RPC).
That's why the trade-off is simpler architecture (generic endpoints are often an unnecessary abstraction) VS decoupling (tailored endpoints require the frontend and backend to be deployed in-sync).
In the long term I foresee RPC to be also used for very large teams. I've ideas around this, stay tuned. I can even see companies like Netflix ditching GraphQL for RPC, although this won't happen any time soon.
In the meantime, RPC is a natural fit for small/medium sized teams that want to ship today instead of spending weeks setting up GraphQL.