The difficulty lies with the fact that @Unsure1045 has gestational diabetes. The mother has high blood glucose levels due to diabetes, but the baby doesn't have diabetes, so responds to the increased glucose by producing higher levels of insulin. Higher levels of insulin inhibit the production of surfactant, making babies of mothers with gestational diabetes have a later lung maturation.
Additionally, surfactant levels normally trigger labour, so the fact that a woman is in labour (in normal physiology, not with labour triggered by infection, etc) means that the baby's lungs are ready.
When a baby is born by C-section without labour, they are being born before their lung development has triggered labour. In other words, their lungs haven't said 'I'm ready'.
Finally, alongside surfactant (which makes the lungs slippery and able to inflate easily), the baby has gunk in their lungs. Natural labour involves contractions, which squeezes the gunk out of the lungs. A c-section overrides this process.
Therefore, a 38 week baby whose mother has gestational diabetes may have underdeveloped lungs, reduced surfactant, and increased gunk, which increases the chance of Neonatal Respiratory Distress Syndrome.
Some babies will be just fine, others won't. You only find out when a baby goes into respiratory distress. You will never know if a baby whose mother received steroids would have been fine without them. Similarly, you will never know if a baby whose mother didn't have steroids and that goes into distress would have been fine if they had steroids. And you'll never know if the baby whose mother had steroids and still went into distress would have been worse or better without them. So you can only work on statistics.