No USB-C hub has FireWire to my knowledge. Hubs are a minefield if you read the Amazon reviews. So are most cables. Some will actually break your device because they try to draw too much power. Some may have 3 USB ports but only power one hard drive. Others don't work with certain brands of hard drives at alll. There's a ton of mis-informion about USB-C out there and the tech press isn't helping.
The article you link to is a perfect example. The new MacBooks don't have USB-C ports. They have Thunderbolt 3 ports with USB-C. It's an important distinction.
If anyone is reading this and wants to play it safe. Stick to official branded adapters like Apple or Belkin. I've actually skipped dongles for most of my stuff and bought replacement belkin leads entirely with USB-C on the end.
As to your original question, can you piggyback the 2 adapters together (Thunderbolt3 to Thunderbolt 2) and (Thunderbolt 2 to Firewire 800) for FW connectivity, the answer is YES. At least so long as you use Apple's adapters.
And yes there are hubs that are Mac compatible that have Firewire connectors like the soon to be released OWC USB-C 13 port hub. (Weirdly this hub only supports USB 3 gen 1 (5GB/s not gen 2 10GB/s) but has FW800 port.
Other things, Apple actually uses the Mini Display Port (MDP) not the standard Display Port for ThunderBolt 1 & 2. And to add to the level of confusion, some of the early Macs only had Display Port protocols and not TB, while later models supported both DP and TB some TB1 and some TB2. Confused yet? The chipsets and active cable actually supported DP via multiplexing DP over TB, on a MDP connector. Huh?
The physical USB-C port is defined as a connector that supports many different protocols. Personally, I use the designation as USB-C with support for various protocols. What protocols it supports is dependent on the computer side chipset, the target device chipset, the cable and various firmware/software along the entire chain.
This is already a world of vast confusion. Bound to get worse.
IMHO Intel and tech writers are wrong to call the port itself ThunderBolt3 port, it isn't, it is a USB-C port that supports the TB3 protocol under Alternative Mode inside the USB-C specifications. Intel makes it seem that it is they who created the physical port and are including USB instead of it being a USB implementers specification that allows TB and other protocols.
Should we call the same USB-C port Display Port; HDMI; USB 3.1 gen 1 or 2; USB 2 or 1.1; Audio Only; or even Power Delivery, if that is the protocol that is being used or supported? Take Apple's own MacBook with USB-C connector that does not support any TB protocols and only supports USB 3.1 gen 1. not even gen 2.
OK, so we are in a world of a physical port being many things but maybe not all things(protocols) capable. Add to this that the entire chain of connections, cables and devices must all be capable of the desired end game in order to work.
If all this isn't bad enough, not all USB-C devices are supported on Macs including TB3 chipsets. Intel licenses the technology and different manufactures have to include Mac support. Some chipsets just don't. (This is often firmware). Intel has a least 3 versions of TB3 chipsets/controllers and Apple even includes some unique firmware codes to prevent malware attacks via TB and PCIe lanes. TB opened up the possibility of low level system attacks which Apple is attempting to prevent. Remember that most TB cables are active cables with chips included in the cable itself. TB3 also has a passive cable mode that limits speed and length, just attempting to hurt your confused brain here
Well anyway, just my 2 cents that the port itself should be called USB-C with whatever protocols it supports, not by the protocol itself. It is ThunderBolt delivered via USB-C, not USB-C delivered via TB. USB-C actually reserves certain pins and wires exclusively for USB and provides additional pins and wires for alternative mode with a data pin(s) that determine what protocols are being accessed.
Hope this helps, Greg
p.s. Take 2 aspirin and don't call me in the morning.