Does WCAG (2.1) apply to native (iOS, Android) mobile apps?

WCAG stands for Web Content Accessibility Guidelines, but it never defines what is meant by "web content".

Many of the success criteria are defined in terms of "user agent" as if they meant a web browser, but the WCAG 2.0 Glossary defines "user agent" again in the terms of "web content", while it also mentions a "media player" as an example of a user agent that "...helps retrieving and rendering Web content". So if a stream of video data is considered web content, then even multiplayer video games can be considered as rendering web content?

Then there is this 2015 document How WCAG 2.0 and Other W3C/WAI Guidelines Apply to Mobile that specifically mentions "...native applications (also known as "mobile apps")", but then it says "[the document] provides informative guidance, but does not set requirements."

I am perplexed.

My question: Does the WCAG 2.1 success criteria apply to native (iOS, Android) mobile apps?