I somewhat agree, because "transparent" isn't exactly true. Popping a drive and putting a blank one in means a resync spike as the new one is filled. With multi-TB drives, that resync time isn't exactly trivial, and a drive failure during resync is certainly a possibility, as there is more activity.
Going with something that can handle multiple failures is helpful, such as RAID6, but you're still increasing risk just by performing your backup operation. In fact, part of the reason RAID6 exists is that there were enough cases of a RAID5 drive failure causing a second failure during the rebuild, and losing the whole array.
Using a removeable drive as a target for backup software, and treating is just like a tape, though, is a very effective solution and takes care of air gap concerns.
The parent post didn't explain any procedure other than a DC sync, which only protects against physical failure at the main DC.