Your solution is more foolproof, but Micro Snitch[1] is worth looking at - same company behind Little Snitch.

[1] https://www.obdev.at/products/microsnitch/index.html

Very very shitty microphones, so the statistical risk is significantly reduced! And the hardware might not support doing that switch in software.

Actually, you can get pretty good quality (You could easily do speech-to-text on the produced audio)... If you want to do a simple test, plug-in your headphones into your microphone jack and start recording away. I just did it why my current cheap Amazon basics headphones and I can clearly hear my speech back. Also take a look at https://www.youtube.com/watch?v=GqNrLfbwAH8, I think that this shows you how to record from your laptop's speakers in Windows using Audacity.

True.

The video: No, it shows how to 'record what you hear' (windows mixer) nothing to do with the speakers.

I would claim that it is impossible to record from speakers that are connected to low impedance running output amps and record from them at the same time.

So if the speakers are playing music they are not recording your sing-a-long also.