Speaking as a network engineer, that’s actually kind of the opposite of the hub concept in the context of network engineering (although it is the way Samsung uses the idea of “hub” for its Family Hub refrigerator).
From an engineering standpoint in home automation a “hub” establishes the network that communicates directly with the end devices. It has matching radios. Your SmartThings hub has radios inside for both zwave and Zigbee. It also has the ability to connect via Ethernet (or WiFi for the V3 model) to the SmartThings cloud, which is how it communicates with the app on your phone.
The SmartThings Cloud (not the hub) is what communicates with all those other third party devices, either cloud to cloud or other company’s hub to cloud.
This diagram is for the new architecture. The SmartThings hub, if you have one (it’s not required unless you have zwave or Zigbee devices that don’t offer a cloud route) is that little square box in the upper left.
So what you were describing was really the big cloud in the middle. It can talk to the SmartThings hub and it can talk to other companies’ hubs through the “SmartThings API,” that gear image at the bottom left of the cloud.
The vast majority of SmartThings customers these days, certainly over 90%, don’t have a SmartThings hub. They have a Samsung smart television or other Samsung appliance. They could also have an Ecobee thermostat, Philips Hue bridge and bulbs, Leviton WiFi or Lutron smart switches, Meross smart plugs, a Ring Doorbell, an Aladdin garage door controller, a Yale WiFi door lock, and a bunch of other stuff, all without ever having a SmartThings hub.
Back in 2015, you needed a SmartThings hub to get started, which is probably where the confusion came. People thought of a hub as being the same as a location or even an account.
But by 2018 with the introduction of the new app that had all started to change. And now way more people don’t have a hub than do.
The new buzzword for all the stuff that happens in the cloud is “platform.” You have an account on the SmartThings platform whether you have a hub or not.
And “ecosystem” is the buzzword for everything you can connect to the SmartThings app: they are all part of the “SmartThings ecosystem,” regardless of brand or protocol. And again, regardless of whether you have a hub or not.
The SmartThings platform has the largest coverage of competitive IoT devices on the market, including Samsung devices and appliances.