SmartThings terminology is rather inconsistent, though to be fair it is also evolving.
In the app we are seeing stock solutions that would be recognisable from Classic SmartThings and that would have just been called SmartApps previously, such as Home Monitor and Lock Guest Access, being bundled together with other stock solutions, such as Find and Cooking, under the Life tab and referred to as Services. Makes you wonder why it isn’t called the Services tab …
SmartThings wouldn’t be SmartThings if Services didn’t already mean something else. Connected Services or Linked Services (the app infuriatingly uses both terms) is still being applied to other integrations like Alexa, Google, Nest and ActionTiles and you’ll find other OAUTH based integrations there as well. The common link there is that they are usually either established from ‘the other end’ or as a consequence of doing something else like Add Device or adding a Voice Assistant (the latter is in the Menu tab).
Last time I read the latest documentation, SmartApps were also bundled under Connected Services, unlike in the app where they are Automations.