Deleting subvolumes - there be dragons

[KC <impactoria@googlemail.com>]

I just read this article here: https://lwn.net/Articles/579009/  which 
states:

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btrfs subvolume delete path

  For ordinary subvolumes (as opposed to snapshots, described below), 
the subvolume indicated by path must be empty before it can be deleted.
---------------------------------

So I gave it a try:

$ sudo btrfs subvolume create /home2
$ sudo mkdir /home2/lalala
< copy a random pdf file into /home2/lalala) >
$ sudo btrfs subvolume delete /home2

And boom! It's all gone!
Even though subvolume was not empty.

So apart from the fact that it looks like the article is wrong here, it 
seems very dangerous to me that one simple command can nuke an entire 
volume, even if it's full of files and folders.

Of course I'm new to btrfs so maybe I'm reading something wrong. If so, 
then please do set me straight.