How does this work in practice using Next.js? My first impression is that if there is a failure/outage in fra1, then dub1 will be used. However I see this, on https://vercel.com/docs/functions/edge-functions#regional-edge-function-invocation

"During regional outage, we have automatic failover to other regions to maintain uptime. This means that Edge Functions are executed in the next closest region. This is applicable for both global and regionally specified Edge Functions. See our outage resiliency docs for more information."

So what is the point of using an array of preferred regions? Does this override the automatic failover?