They still are in SaaS - with 'Workplace by Facebook'

The article is referring to IaaS from my initial read.

https://www.facebook.com/workplace

Parse doesn't seem to have been any kind of general-purpose cloud at all.

Rather, it appears a highly targeted backend specifically for mobile apps only. The article says "back-end services for data storage, notifications and user management".

They're some pieces of a cloud, for sure. But it's worlds away from the general-purpose offerings like AWS and Azure that the author is talking about. So not surprised the author didn't bother to mention it.

I am kind of amazed the author didn't mention Parse once.

The difference is that Parse ran on AWS. In my opinion, the real reason Facebook isn't in the cloud business, and why Parse was eventually shuttered, is that Facebook will never allow external code to run anywhere in their network.