Interesting video, but it didn't tell me why rollable phones aren't a thing. It doesn't appear any more flawed than the foldable concept.
The impression I got was "too many parts, too much to go wrong, too expensive to build".
It doesn't rule out that other people might have better ideas, but it does suggest why LG decided it wasn't worth it.
I think the article gets at it indirectly: a complex mechanism with multiple motors, tracks, arms, etc, substantially more complicated and thus more failure-prone than any folding phone ever and also substantially more expensive to make.
Additionally, the flexible screen is on the outside which will quickly get damaged since it is made of soft plastic. It's too fragile for something that lives in your pocket every day. All modern foldables have the folding screen on the inside to keep them protected, and a standard glass screen on the front.
It slides behind a glass panel on the back, so I don't think that's true.
The whole display is plastic, including the part on the front that doesn't wrap around. Yes the part behind the glass panel on the back would be protected, but the front of the phone wouldn't be.
Yet they still make trifold phones where one of the folds is on the outer side...
"they" being Huawei, and their phone suffers from the same problem, the main display can be easily damaged by dust, dirt, or just your fingernails pressing into it. Notably Samsung's trifold kept the folding display entirely inside when folded, presumably to avoid this problem.