No, you are not missing anything. I just reviewed the category selection interface within the Auctiva mobile app and confirmed that the category options are not alphabetized like they are on the regular Auctiva.com website. I have made note of this and we will look into the possibility of alphabetizing those options within the mobile app for a future update.
While it is certainly possible to navigate to the Auctiva.com website through Safari on your iPad, there are a number of known issues that will likely prevent you from being able to use the regular site at the moment. Most notably, an error message will likely be generated when you attempt to access the Login page.
We currently hope to be able to update the Auctiva.com website such that sellers will be able to use it effectively through the iPad in the future, but there is a good deal of work to be done before we get to that point and I'm not sure when we may be able to reach that goal at the moment.