Github user twalthr commented on the issue:
https://github.com/apache/flink/pull/5662
Thanks for the comments @xccui. It's never to late for feedback. Sorry,
maybe I merged this too quickly. We still need to call
`builder.forJsonSchema()` if the schema contains a `proctime` attribute. The
most common use case will be to extend the format by time attributes. With your
approach the format would contain an additional timestamp that is definitely
not part of the format schema.---
