I’m not sure what you mean. Flexible OLED displays have been around for a while and foldable devices are just an example of the technology in use, but we’ve had them in consumer products way before that (phones with curved edge displays, for example). The potential for flexibility has always been intrinsic to OLED displays because they don’t need a backlight. The reason our phones don’t bend and flex like the “device” in the video isn’t because of the display, but because the battery, processors, ram, speakers, ports and all other components are not flexible and won’t be for a while. The device in the video does not include those, there is a ribbon cable coming out of the bottom connecting the two screens to the actual hardware.

I’ve had this issue with Samsung phones and tablets I owned in the past. Working as an app developer I still see this kind of problems on heavily oem-customized versions of Android.

Personally I “solved” this by switching to Pixel phones which in my experience don’t slow down even after 3-4 years of usage and updates. I believe this is true in general for phones that stay as close to AOSP/stock Android as possible.