Hello, sort of,… Postfix have internal rate limiting service, but from log you have submitted, does not show you are hitting those limits. Log line for those would be something like warning: Connection rate limit exceeded: XX. Those lines from anvil service should be only statistic information.
But you are right, while every connection seems to by from same IP, from your gateway, you can be hitting rate limit.
But as far as I know Mailcow use Postfix default that would mean no limiting over those anvil 60s because smtpd_client_connection_rate_limit (default: 0) and max 50 simultaneous connection because smtpd_client_connection_count_limit (default: 50) So unless your are flooded by connection, anvil does not show, you are not rate limited.
As always I can be wrong.
Source: https://www.postfix.org/postconf.5.html