Sam, it says about the Ugos that they were Matzos. I believe the above explanations cover Succah as well as Matza.
Ubiquitin, it seems like you added that ‘(to us)’ because you realize there is a big difference. We must follow and can’t change Halachos based on Aggada or Sohd or rationalistic reasons. This is because we can never really be sure we got to the bottom of it. In fact, we can assume we don’t, as it says, Rechava Mitzvas’cha Meod. And besides, we don’t have permission to change what is given, even if it would otherwise be justified.
The Avos didn’t have any of these issues. Even if the Mitzva is deeper than their understanding, they didn’t lose by doing it according to their understanding.
In fact, the Torah was given to us. Therefore, whether we understand it or not, when we perform a Mitzva, it accomplishes what it has to. The Avos, on the other hand, had it the other way around. If they acted upon what they didn’t understand it would have been foolish.