That's part of the sync step. Basically it stores the "current" state and will mirror that to all devices.

I would class a backup differently. Say someone grabs your phone and deletes your conversations (or you accidentally swipe the wrong way). How do you get those back? Because the sync service immediately removes them from all devices with no way to roll that back.

The author is ranting that he doesn’t know how 2-way syncing works, I for once would be pissed if I deleted a message on my iPhone and its still on my iPad/macbook. You’ve made a conscious decision to delete your messages and know you blame the manufacturer because you changed your mind? Its a ridiculous premise

I think the authors point is that iCloud is many things. It's for backups AND for 2-way sync, and when you have what activated, and their connection, is not absolutely clear for the average user.

Yeah this is the issue. Is it a backup or is it sync? It's not like "left for backups, right for sync", it's just on or off for "iCloud". Which isn't even consistent across apps.

You delete an entire conversation in iMessage by swiping to the left and then tapping a button on the left, FYI. Which is easily fumbleable, or possible to trigger with a wet screen, and is what happened to my girlfriend.