Not specific to any model but for most Lenovo devices, including phones.
For some reason, some brands, mainly Chinese ones, include two internal partitions. Second partition is shown as "USB Storage" or at least that is what is shown in the "Move to USB Storage" button in App Manager.
It's like a bad joke, because you can buy the larger SD Card the device support but there are no "Move to SD Card" button in App Manager, in it's place you have the "Move to USB Storage" button that does nothing useful because the internal partition detected as "USB Storage" is 1 GB only, sometimes I have seen 2 GB but it still is useless. So you end with a device that you can install at most 5 apps, less if you install Facebook that takes about 300 MB.
Is there a way to get the "Move to SD card" button to show in these devices?
Do they do this to prevent you from moving apps?
Please, do not suggest flashing with alternative ROM. I would do that gladly if the original ROM was around in case of disaster. But as the original ROM of these devices is nowhere to be found then flashing is too risky.