You had a small fallacy in the middle, when you said "assume the negative claim", you then made a positive claim.
"subjectivity is not explained by information processing theory" is a positive claim, but you said it was negative. I know it has the word "not" in it, but positive/negative doesn't have to do with claims for or against existence, it has to do with burden of proof. A negative "claim" isn't actually a claim at all.
The negative claim here would be "subjectivity may not be explained by information processing theory". People usually have more understanding about these distinctions in religious contexts:
Positive claim: god definitely exists Positive claim: god definitely doesn't exist Negative claim: god may or may not exist.
The default stance is an atheistic one, but it's not "capital A" atheist (for what it's worth I do make the positive claim against a theological God's existence). Someone who lacks a belief in God is still an atheist (e.g someone who has never even heard of a theological God), but they're not making a positive claim against his existence.
So the default stance is "information theory may or may not account for subjectivity", we don't assume it does, but we also don't discount the possibility that it does as necessarily untrue, like you are.
If you notice, you made another mistake, you misread what I was saying. I never made a positive claim about subjectivity being information processing. I only alluded to the possibility. You on the other hand did make a positive claim about subjectivity definitely not being information processing.