Agreeing with this, expanding a RAID array is not necessarily impossible, with something like RAID 5, and the right RAID setup, you could theoretically add an identical disk without wiping it all in the rebuild. RAID 1, you’ll 100% need to copy the data somewhere that isn’t the 2/4 disks in the meantime. In an environment where storage is expensive, RAID 1 is not suitable imo.
ZFS makes it so easy though. Throw a mismatched disk in? No big deal, it’s in your pool now. Want double parity for extra peace of mind? You can do that. It self-heals so you don’t need fsck, its maximum limits are too big to realistically matter on human scales, and the documentation on it is pretty good.
The field of artificial intelligence has also made incredible strides in the last decade, and the decade before that. The field of artificial general intelligence has been around for something like 70 years, and has made a really modest amount of progress in that time, on the scale of what they’re trying to do.