const HeadersSchema = z.object({
  // Header keys must be in lowercase, `Authorization` is not allowed.
  authorization: z.string().openapi({
    example: 'Bearer SECRET',
  }),
})

The above gives me this :

{Authorization: 'Bearer SECRET, Bearer YOUR_SECRET_TOKEN'}

I guess it is being handled by default. So, I had to replace it with
authorization: z.string().optional()

Now it works fine and shows {Authorization: 'Bearer YOUR_SECRET_TOKEN'}

I suggest fixing this in the docs to help others avoid this issue.