Fiori (in SAP context) means several things:
(Some of the infos may reflect a more or less current state of the art and may have been different in the past and may change in future.)
- Fiori Apps (or sometimes called SAP standard Fiori Apps) is a set of (several thousand?) Apps developed and offered by SAP. This includes Fiori Apps for various businesses (like retail) or various departments (like HCM) - See SAP Fiori App Reference Library
- Fiori Launchpad (FLP) is a Fiori App by itself, which is configurable using various methods. FLP exists for ABAP, SAP Enterprise Portal, SAP Cloud Portal, SAP Cloud Foundry and is configurable in different ways in these systems. Intent based navigation that you linked above is one of the ways in an ABAP System
- Custom Fiori Apps are SAPUI5 Apps that follow the Fiori Design Guidelines, as stated by @sap-fiori-crew
- also native mobile libraries like Fiori SDK for iOS or for Android will produce native Fiori iOS apps (or Android, respectively)
- Some non-ui5 Apps like SAP Mobile Cards or Mendix Apps with Fiori Theme are considered Fiori apps by SAP
All in all, currently, SAP states that SAP Fiori is a user experience (see, e.g. this roadmap, page 11)
From the technical point of view, an ui5 app must at least use the Component Paradigma to be seamlessly integrateable inside a Fiori Launchpad.
For the rest of the answer, I’ll refer to any ui5 app that implements a Component as “Fiori App”
As for your original question, and the link you used, I don’t see any technical reason, why a sapui5 app, that implements a component, shouldn’t be callable using intent navigation.
You can configure a tile in FLP to call a certain Fiori App. Or to call a certain action of a semantic object. That action of that object is configured to call a Fiori App using Target Mapping. The good thing is that you can call such an action on such a semantic object from any other app without knowing which App will actually be called. This allows a customer to replace an App by changing a single target mapping rather than finding and extending all other apps that are calling the one replaced app.