Shared flow working as flow callout but not in flow hook

[sk123]

I’m trying to use a CORS policy in a post-proxy flow hook so that CORS headers get set even if there is a fault raised in the proxy. In the debug trace, I see the post-proxy flow hook being called but the CORS headers don’t get set. If I attach the same shared flow as a flow callout, the CORS headers get attached (for successful requests) as expected. I confirmed the flow hook matches the environment I’m testing in (eval org). Any pointers on how to debug further?

[sk123]

Attaching the debug trace as well.