One thing that raidz has going for it over a block level raid is that zfs knows which blocks are in use and recovery does not need to read all blocks on all disks to recover.

Zfs also prioritizes user reads and writes over recovery (resilvering), which may not be universal practice with RAID.

It's certainly still the case that if your redundancy drives failed, you're at greater risk of data loss, and IMHO, disk failure rate during repair is higher than base rate: maybe from extra use, but also because of the risk of correlated failures --- if your environment contributed to failure of the first N disks, the other disks were also in that environment and may be about to fail.