I found a good reason to have coupling if ref level is set to 20dB or higher
The noise floor with the widest RBW is, with a ref level of 20dB just visible if attenuation is set to 10 dB
So if a user sets the reflevel to 20 or 30dB, applying a minimum automatic attenuation of 10 or 20dB does not harm as you are not able to see the noise floor so an elevated noise floor does no harm and it protects the tinySA.
