Yeah actually it would. On my Kenwood TS480 and TS590 enabling the noise blanker absolutely destroys the selectivity of the radio the same as it does on pretty much everything other than full SDR radios - I may have to do another Youtube video... Lowering the sensitivity would leave the radio prone to interference from strong nearby stations such as those in the broadcast band above 7.200. Also you have to remember the 991 doesn't have anything like the filtering that the big Yaesu does. It certainly doesn't have bandpass filters for each ham band.