App Download and "Other" Memory Usage

For a month or so I've noticed that my iPhone 5s "Other" memory was on the order of 6gb... Deleted texts and emails attempting to reduce that size, to no avail...

Today I noticed that an App (Numbers) that had begun to download from the App Store (about a month ago), had not finished (WiFi was required for the large download, but had been turned off and on several times, but not long enough for the download to complete). It wasn't obvious to be that Numbers hadn't finished downloading...

I deleted Numbers from the iPhone, and installed it from iTunes on my iMac.

Upon the deletion of Numbers, my "Other" memory usage went from 6gb down to 2.25 gb, which was reasonable with some large maps and Good Reader docs I have on the phone...

The Numbers app is about 224Mb in size... So, it appears that the iPhone sets aside a very large part of memory for an app as it downloads, and then clears that memory once the app is installed...(though the amount cleared was on the order of 17x the size of the Numbers app...)

I notice a similar usage of Time Machine storage space... Small Time Machine saves require very large amounts of HDD space to be reserved for the backup... Wonder if the same logic is applied to the iPhone... Or perhaps every time WiFi was turned on and Numbers would reattempt to download, the amount of Other memory it required from the iPhone would increase...?

Anyone else noticed this behavior?

Bob