Even if that is true, ZFS disks tend to wear equally across a pool (by design). The point about RAIDZ2 is that after one drive fails, the resilver creates stress on the remaining drives, and the likelihood of a 2nd failure is high during this process. That said these are small drives despite the width. On my own 5x 4TB drives I opted for RAIDZ1, but after I populated the system I had 2nd thoughts and wished I had adopted RAIDZ2 instead but it was too late. So I purchased a one-time 500GB online storage in order to back-up my critical data as a 2nd line of defense.
Summary: If it were me I would use this point about enterprise reliability to forget a hot spare and do 10x RAIDZ2.