Saw this in the EE blog post
RAIDZ Expansion allows RAIDZ (Parity) vdevs to be expanded by one drive at a time, ideal for small footprint systems looking to expand incrementally. This feature also permits 2-drive RAIDZ1 systems, ideal for home users who want to start small on a budget.
Did not know about 2-way Z1? Is that a thing now? Good if it is.
What about 3-way z2? (Would be nice to have a degraded 3-way ;))