As soon as flexible screens become a thing, your phone and your tablet become the same device; you just unfold it when you want a big screen.
In light of this, the size argument being made in this article is not really meaningful in the medium-to-long term, unless these kinds of flexible screens never happen. (But they are being actively worked on, so.)
I think this is spot on. I am not sure how long it will take but there will be a big revolution in screens, like the CRT to LCD one, in the next 20 years and it will be around flexible and expandable displays. Possibly what we know consider to be a screen will be totally changed.
In light of this, the size argument being made in this article is not really meaningful in the medium-to-long term, unless these kinds of flexible screens never happen. (But they are being actively worked on, so.)