The iOS App SDK is intended to be used for enterprise apps distributed via MDM. This is the intention and this process is supported.
Distributing FM iOS Apps in the AppStore can be done. I have done a number of them and so have others. There is no support from FM for this. They will not help you through the submission process or help you work with xCode to set the right things for the app store to approve the app. Therefore because there is no support, it is not recommended.
Like bigtom writes there is not problem for you to add a solution into Apple App store, but it is totally up to you to handle your app from the moment you get it up on AppStore and FileMaker take no responsibility for your code.
Also when handling new versions of apps, depending on the size of your solution getting data from earlier version on the users device into a new version is something you have to handle inside your solution and that could be a little bit tricky.
Depending on what you do, Apple may reject your app and FMI is not responsible.
And if the solution would connect to your FM server, what would happen if 10000 people try your app at once?