Reached out to MS support. For my particular case, this was the reason:

Azure Event Hubs typically counts all events that are sent to the hub, including those that may have failed to be received due to various issues. This means that while the metric reflects the total number of events sent, it does not differentiate between successfully received events and those that failed to reach the Event Hub due to network issues or other failures. If the entire batch fails due to a transient issue (like network problems or throttling), the system may attempt to resend that same batch. Each retry counts as a new ingress event (regardless of the fact that it may be a batch with multiple events), leading to an increase in the total number of events sent.