Write huge amount of data to device' hard disk within seconds in iOS?

Question

Has anyone seen battery doctor app? It increases the device used disk space exorbitantly within few seconds. Suppose, If my 16 Gb iPhone has 9 Gb free space and I run a scan with that app, It raises my used space to full 16Gb in 6-8 seconds, the used space of device becomes 16 Gb and free space becomes 0. Then at the same speed it removes all the data from the device and used space becomes less than 9 Gb.

How is that possible? Even when we write data to device with Bluetooth or USB it takes a lot of time, and this app is doing that within 10 seconds.

Answer 1

All it removes is temporary data

stored in the form of cache
system junk
trashes leftover
logs .
If you ever try to delete data stored on device like images, movies, it will take long..
I am using clean my mac and it works the same...