The buckets an existing connection can see

Names only, read through a connection this org already has, so the next bucket can be picked from a list instead of typed. Empty is ordinary rather than an error: an org with no connection on that provider, an AWS role granted before s3:ListAllMyBuckets existed, the bucket-scoped IAM policy we print, or an R2 token scoped to one bucket. The form falls back to a typed name in every one of those cases.