If it were included in this paragraph, it would become a factor that the commission would have to consider in deciding whether an application is admissible.
With your permission, I would add that the factors set forth in the exemptions are based on the relevant case law in this matter. Ontario's Superior Court of Justice rendered a decision in the McArthur affair that was appealed to the Court of Appeal for Ontario; the Supreme Court declined to hear the appeal. The Superior Court had explained that certain cases at times required an investigation:
“when considering whether or not an [accused] has exhausted his or her rights of judicial review or appeal, a flexible approach must be taken, albeit one that is consistent with the intention of Parliament”.
Essentially, the purpose of the courts isn't to conduct investigations but rather to decide issues of law. Consequently, if an issue of law has to be decided in the case, the appropriate path is definitely to file an appeal.
However, according to the Superior Court, when relevant fresh evidence is required to establish that a wrongful conviction occurred as a result of a miscarriage of justice, it is the responsibility of the Minister of Justice, and potentially the new commission, to conduct investigations in order to gather that fresh evidence so it can be considered in the context of the entire case.
If an individual hasn't already exhausted an initial appeal, this is a relevant factor to be taken into consideration.