Why does a tumble drier tumble when moisture extraction not running with delay start?

[ericmark]

Due to solar panels, battery, and off-peak tariff I use the delay start on tumble drier, washing machine, and dishwasher, both the tumble drier, and washing machine, will rotate the drum every so often while waiting for the time to start, but the washing machine does not tumble clothes every so often when completed the cycle, and they are in a drum just the same as when in the tumble drier before the cycle starts, I could see if using iron dry option a tumble drier would tumble clothes after the cycle had finished, until door opened, (which it does not do) but why before it starts?