Why are sync frequency changes not seen immediately on the sync schedule?
The sync scheduler is based on the destination warehouse timezone. The starting point is always at midnight plus an offset of +0 to +59 minutes. When you change the sync frequency, it will take effect immediately based on the midnight starting point.
If sync is set to run every 6 hours, changing the sync frequency from 6 to 8 hours will cause the next sync to run at 8 AM.