This detection was added in Anti-Beacon 6.7.
Anti-Beacon treats this as telemetry because the setting controls cloud-backed speech and input personalization. Microsoft says that turning on Online Speech Recognition lets apps use “Microsoft cloud-based speech recognition” and that, when those cloud technologies are used, Microsoft will “collect and use your voice recordings” (Microsoft Privacy Statement). Microsoft also documents enterprise controls for allowing users to enable online speech recognition services (Microsoft Learn: Windows Privacy Compliance Guide).
Anti-Beacon disables Windows Online Speech Recognition and input personalization so voice recordings are not sent to Microsoft’s cloud speech-recognition service through this feature.