Yeah run diff is really only usefull over long periods of time. It's not something that matters in small samples.
Virtually every team's record in MLB is within 5 games either way of their expected W/L based on run diff, and the majority are within 1-3 games which is completely expected.
Very few are exactly matching (Milwaukee, Colorado, Philly, Minnesota, and Detroit)
The biggest variances are Tampa (-6 wins vs expected), White Sox (-7), Rangers (-6), and the Braves (-6),