AWS Config Resource Update Latency?

I am creating a customized rule to check the S3 bucket policy in my AWS account. The lambda has been created, and the Config Rule being configured as "When configuration changes". From the CloudWatch Log, I can see it has been triggered by the rule. However, once I've updated a bucket policy and re-evaluate the rule, the event passed to the lambda is still showing the bucket policy of the previous version. Seems to me as if there is a update latency between the real bucket policy and the info recorded in Config Resource, right? Or there is another explanation of this phenomen?