If someone wants to use the Spine Runtimes, the Spine Runtimes license applies:
Spine Runtimes License Agreement
There are two options:
1) They can license Spine, which grants rights to build any number of applications using the Spine Runtimes. In that case, see Section 2 of the Spine Editor license:
Spine Editor License Agreement: s2
2) Otherwise they can include the Spine Runtimes license with their applications, which means each of the users of those applications needs a Spine license.
The text in your original quote is talking about Section 2.3:
Spine Editor License Agreement: s2.3
That allows you to license Spine, build an app, and then sell or give the app to 3rd parties, then as long as those 3rd parties don't modify the app, they don't need a Spine license.
When you give someone Spine assets for them to build their own app using the Spine Runtimes, then they need a Spine license since they are building a new app using the Spine Runtimes.
To be clear, you can sell or give your Spine project file or exported images, video, or data to others. The others only need a Spine license if they want to build an app using the Spine Runtimes.