Why the migrate apply do not run in the same transaction?

[XiaoXiaoSN]

I'm trying to understand the sqlx::migrate::Migrator and sqlx::migrate::Migrate mechanism, but I have a question:

https://github.com/launchbadge/sqlx/blob/v0.6.0/sqlx-core/src/postgres/migrate.rs#L217-L247

Why we don't put user migration.sql and _sqlx_migrations record in the same transactions?

I mean shouldn't it be like this?

            let _ = tx.execute(&*migration.sql).await?;

-            tx.commit().await?;

            let elapsed = start.elapsed();

            // language=SQL
            let _ = query(
                r#"
    INSERT INTO _sqlx_migrations ( version, description, success, checksum, execution_time )
    VALUES ( $1, $2, TRUE, $3, $4 )
                "#,
            )
            .bind(migration.version)
            .bind(&*migration.description)
            .bind(&*migration.checksum)
            .bind(elapsed.as_nanos() as i64)
-            .execute(self)
+            .execute(tx)
            .await?;

+            tx.commit().await?;

Am I missing something ? 👀