On Oculus Unity Integration v1.43, ONSPAudioSource.cs includes a static method that gets called as a RuntimeInitializeOnLoadMethod and calls platform specific code e.g. OSP_SetGlobalVoiceLimit(ONSPSettings.Instance.voiceLimit)
Since this is a runtime init method, it will get called just by the fact that it is present in the project, even if you are on a platform that is not using the spatializer. Please add some preprocessor platform definitions around the contents of this method to handle this.