"For me event-sourcing is a historical layer below your existing database that allows you to replay the sequence of events that got your database to its current state."
Yeah, that's essentially what it is. For example, you can build event-sourcing by tapping in to the log-shipping facilities that postgresql offers (set wall to logical, and assign a replication slot to it)
A transaction log is too detailed and specific. Typically an event log lists actions from the business domain rather than what got affected. It should explain what happened, not how it happened.