@yonkiman The output of OBS is not the same as the monitoring device. "Output" means the final mixed audio that goes to the stream or to the recording. Monitoring is sending individual sources to some monitoring device before mixing. Can be configured in Advanced Audio properties of OBS. If you send multiple sources, they are mixed, of course, but as far as I remember, audio filters are not applied. It's not the same audio as the "Output".
Your software is just grabbing audio from devices (also provided by vb-audio or voicemeeter for free/donations) and apps (that's a new functionality, but also provided by the application output audio plugin of OBS). It isn't able to grab the "Output", because this is directly written to the stream or to the file, not going through the audio subsystem of Windows.