Does a database transaction rollback if a PHP/Gateway timeout / connection dropped/lost occurs?

I am using Drupal behind a reverse proxy/cache layer (e.g. Cloud Front/ Akamai) and sometimes the service goes quite slow (so I get a Gateway timeout, for reasons such as too many people are using the servers) or a something bad happens in the server farm (docker micro-architecture) and so I get a 502 Bad Gateway.

Do we know if a database transaction will roll back in such cases? This is especially relevant when doing 800+ entity updates via the Batch API.

E.g. (based off mock code: https://www.drupal.org/docs/drupal-apis/database-api/database-transactions)

$transaction = $connection->startTransaction();

try {
  // Do some thing that writes to the database.
  $entity = create_some_entity();
  $entity->save();

  // Pretend a 502 Bad Gateway or Gateway timeout happened here.

  // Do another database write that depends upon the first.
  $dependent_entity = update_dependent_entity($entity->id());
  $dependent_entity->save();
}
catch (\Exception $e) {
  // There was an error in writing to the database, so the database is rolled back
  // to the state when the transaction was started.
  // Not sure if catching an exception will do anything here.
  // (since no exception is expected)
  $transaction->rollBack();
}

// Commit the transaction by unsetting the $transaction variable.
unset($transaction);

A transaction is only rolled back when Transaction::rollBack() is explicitly called. In case of time outs, that doesn't happen.
Actually, in that case, the database changes aren't even committed, since that only happens when Transaction::__destruct() is called.

public function __destruct() {
  // If we rolled back then the transaction would have already been popped.
  if (!$this->rolledBack) {
    $this->connection->popTransaction($this->name);
  }
}