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

The definition of "web content" by WAI that you posted is clear enough - WCAG does not apply to native mobile apps.

1. Does WCAG 2.1 apply to mobile apps?
2. Does WCAG apply to native mobile apps?
3. Do apps need to be WCAG compliant?

Does WCAG 2.1 apply to mobile apps?

WCAG—specifically WCAG 2.1 AA—enables organizations to improve their existing web content and mobile apps in order to comply with legal requirements and make their products accessible to all.

Does WCAG apply to native mobile apps?

The Web Content Accessibility Guidelines (WCAG) have been the standard for digital accessibility the world around for two decades. While it wasn't created to specifically govern native mobile applications, many of the guidelines can be applied either directly or with some thoughtful interpretation.

Do apps need to be WCAG compliant?

While WCAG conformance is voluntary, ADA compliance is mandatory. The WCAG framework provides the best roadmap for designing mobile content with an accessible mindset.