Shem Chometz/Shem Ochel

In Pesachim 21b Rava says that if chometz is "scorched" (chorchu) before Pesach it is mutar on Pesach. Tosafos there says the case is where it was damaged to the point that it is not even edible by a dog. He proves this from the case of Pas Sheipsha (bread that got moldy) where the halacha is that it needs to be unedible to a dog to be mutar.
R' Boruch Povarski in his chiddushim asks on this from the general halacha that we find by neveilah that you only need it to be unedible to people to be mutar. So why on Pesach must it even be unedible to a dog?
He anwers from R' Chaim that for Issurei Achilah it is true that you need it to only be unedible by man. However, by chometz it is not only an issur achilah. There are other issurim as well. Therefore, you need to get rid of the "shem ochel" completely, and you need it to be unedible even to a dog. (By other non kosher foods you only need to remove the maaseh achila, but the shem ochel can still be intact.)
Rashi on the sugya describes the case of chorchu as "losing its taste and appearance". It is mashma that it still hasn't reached the level of unedible to a dog. Many achronim in fact say that it need only be unedible to a human. The question on Rashi then, is from the case of pas sheipsha, the moldy bread. Why over there must it be unedible to a dog and here it need only be unedible to a human. This question is asked by many of the achronim on Rashi.
In terms of the mashmaos of Rashi it is possible Rashi is saying an even bigger chiddush. It could be that "losing its taste and appearance" is still even edible to people. Of course, the difficulty on Rashi would remain in an even stronger fashion with this understanding. The Meiri in fact does bring opinions that seem to hold that in this case of chorchu it is still fit for human consumption, and nevertheless becomes mutar. The question remains, why?
Perhaps we can suggest in Rashi that in order to transgress the issur of chometz the chometz must fulfill two dinim. First, it must have "shem ochel", it must be considered a food. Second, it must also have a "shem chometz", it must still be considered chometz. If so, by moldy bread it is still "bread", only unedible bread. Therefore, it must be unedible even to a dog in order to not be considered food anymore, as per R' Chaim's understanding. However, by chorchu even though it is still edible, and considered a food, it has no appearance or taste of chometz. It loses the shem chometz. Therefore it is mutar even though it is entirely edible.
The real chiddush that we are suggesting then is that the shem ochel and the shem chometz are entirely independent. Moldy bread can lose it's shem ochel even though the shem chometz is still there. Once that happens it becomes muttar even though the shem chometz is there because the issur of chometz on pesach is only on edible chometz and not unedible chometz.