Is the deadline extension applicable to belated returns as well?

The government’s notification clearly says it applies to “returns due on July 31.” That means belated returns are not included. If you miss September 16, you can still file belated return until December 31, but with penalty.

No, the extension is for original returns due by July 31. Belated return deadlines are usually December 31 of the assessment year. If you don’t file by September 16, your return becomes belated. So, extension only shifts the original return filing date, not the belated one.