Why 45MB Unallocated space at the beginning of a Silicon Power Marvel M70 64GB Flash Drive AND Why Drastically different sector counts?

Solution 1:

Some flash drives (and even external HDDs) have built-in software. These drives are made to look like 2 devices to the OS, the first is presented as a CD-ROM and the second is presented as a normal read/write mass storage device.

This is not partitioning as understood/done by the OS - it's done on a lower level - it's controlled by the microcontroller in the USB device.

Utilities from device manufacturers (often in Chinese) do exist to change this arrangement--and you have to use one compatible with the microcontroller--and they are difficult to find and use.

I'm betting this flash drive at one point was destined to have built in software on it, but the manufacturer changed their mind for whatever reason.

So the unallocated area probably was a fake "CD-ROM" area containing encryption or backup software from another SKU of drives this manufacturer (or possibly another manufacturer) offers.

The manufacturer probably had an oversupply of these particular devices or some other related economic condition, then ran a utility to reconfigure the flash arrangement and remove the "CD-ROM" partition, but didn't bother to wipe this section of flash before packaging.

You should run TestDisk on the unallocated partition and see what you can find!