You have misunderstood the article. It is not advocating for the return to single address space systems. It is advocating for potential alternatives to the linear address space model.
Here [1] is an operating system that I think fits under the description of what you were talking about
The more I research Singularity, the more I like it. I deep dived into all the design docs years ago and the amount of rethinking existing OS infrastructure is astounding.
https://en.wikipedia.org/wiki/Singularity_%28operating_syste... [1]