I have just noticed this on one batch running on https://importer.collectionspace.org/
The start/end times for preprocessing are as expected:

Before I clicked backward to the Preprocessing step, the Processing step was showing:
Job created at: August 4, 2021 7:27pm
Job completed at: August 4, 2021 4:33pm
After going back to the preprocessing step and return to the processing step, I see:
Job created at: August 4, 2021 3:27pm
Job completed at: August 4, 2021 4:33pm