The author wants zfs to support growing and shrinking pools in a specific way that it doesn't support.
However it's clear from the docs that you can grow zfs pools by adding new vdevs. Shrinking a pool is not possible.
In practice I haven't seen the inability to shrink pools as an issue. I simply do not create pools from entire disks and use partitions instead. For example each drive is split into 5 partitions. And if I need to grow a pool I add another partition across all my disks to the pool as a new vdev.
This also allows me to have multiple pools on each system that have different Raid-z levels based on different app reqs.
It is clear from the article that I acknowledge this fact but it is a more convoluted, less flexible solution that wastes space. BTRFS shows how it can and should be done.
However it's clear from the docs that you can grow zfs pools by adding new vdevs. Shrinking a pool is not possible.
In practice I haven't seen the inability to shrink pools as an issue. I simply do not create pools from entire disks and use partitions instead. For example each drive is split into 5 partitions. And if I need to grow a pool I add another partition across all my disks to the pool as a new vdev.
This also allows me to have multiple pools on each system that have different Raid-z levels based on different app reqs.