Articles like this are really just propaganda (wishful thinking) trying to soften the blow of Baumol's Cost Disease:
https://en.wikipedia.org/wiki/Baumol_effect
Industries that benefit heavily from automation reduce costs over time. Industries that rely heavily on services (that require people to perform them) increase costs over time.
If you can somehow convert a big chunk of your economy into services from automated production, you can smooth out the difference in that economic curve. In theory, that means the rich (capitalists) can continue to get richer while everyone else's salaries flatten out.
It's total bullshit. The only logical end result of such a situation is the rich getting eaten sooner rather than later.
Smart rich people are (right now) lobbying to get their taxes increased to pay for a better social safety net. Stupid rich people are lobbying for bullshit like converting everything into a subscription economy.
Simple: Exfat does not support symbolic links. So every file that's just a symbolic link on your btrfs filesystem is getting copied in full (the link is being resolved) to your Exfat drive.
Solution: Don't use Exfat. For backups from btrfs, I recommend using btrfs with compression enabled.
Also don't forget to rebalance your btrfs partitions regularly to reclaim lost space! Also, delete old snapshots!