There could be, for some children.
Another hypothesis is that the symptoms you occasionally experience as inattentive may actually reflect challenges in receptive language, which would fit with lower performance on Co than Si/Vo, as Co requires understanding a longer, more complex language stimulus (sentence-length questions, some of them fairly long, compound/complex sentences). That is, it may be that he is not understanding/following directions because he is not attending through the whole direction, or it may be that he is not understanding the language itself, because there are too many words and sentence structures to process.
This is also where the other poster's reference to auditory processing disorder comes in, as that is another condition whose symptoms overlap ADHD.
So far, everything you have reported could be consistent with any one of 1) ADHD, 2) CAPD, 3) receptive language disorder.
Oh, and a filter is a personally-fitted ear canal piece that selectively screens out certain frequencies, in order to make the auditory environment less chaotic for the wearer, with the primary objective of improving their experience of speech clarity, and the secondary objective of reducing sensory overload.
