I think they're maybe alluding the fact that if you have a backup system which fails when you need to use it (e.g. your Time Machine backup turns out to be corrupted, which quite a few people in the comments seem to have experienced), you'd wish that you'd paid money to have a backup system which worked instead.

You wouldn’t usually just have a single backup system, If the disk image that time machine is stored on head issues that would usually be picked up at the time. It was being mounted and either repaired or you’d get less that the discount is corrupt. it’s never going to be as good as something like Borg where you’re doing regular data consistency checks but you can still check the fast system of the DMG as frequently as you wish.