This is just a limited perspective by having a look around the code for publish and AMQPConnectionException but without full knowledge of this extension and especially rabbitmq-c: the exception is only thrown for specific stati returned by the library client, which are all related to the connection to the server. So I think it's fair to assume that: "no connection -> nothing published"
Reference: https://github.com/php-amqp/php-amqp/blob/latest/amqp.c#L493

Bu this might also be of interest to you: we were running into the exact issue your contribution aims to fix (retry on lost connection). However, we are getting a AMQPException instead of AMQPConnectionException. Reason is the AWS Load Balancer which results in a "a SSL error occured". Same in this issue: symfony/symfony#48241
That's why I created this PR here to also treat SSL and TCP errors as a AMQPConnectionException: #571
And thanks for the fix, by the way! These errors caused quite some headaches in our team.