I'm facing the same issue, I've made an app that uses public APIs from the Nasa. Before I started the app I couldn't find any related app after long searching with all the keywords I could think of. Then my app was approved for several versions, then I started to make more apps doing the same but for different parts of the world. Also approved several versions.
Then suddenly while updating them I got rejected under this code, they said you must make 1 app instead of many but with In-App-Purchases for the other regions. So again one more week of programming, my single app with 8 IAP was ready. Submitted and again rejected under the Design Spam reason. They would not tell me why, so I started searching the app store again (horrible search by the way) and after scrolling through 1000s of police radar apps and games I found 2 apps that did nearly the same as my app, only not so nicely done. They rendered a 3d world instead of using Apple maps and my App makes you go directly zoomed in to one country. Plus the way I present the info in the pins is 10 times more functional then the other apps.
My observations and remarks here are:
Apple seems to get strict with this rule, which makes it very hard to create something original especially with this horrible search of the app store, before creating an app spend most of your time searching for a similar app.
Having an app approved does not guarantee anything for future updates of your app.
Try to make the first release of your app as good and tested as possible so that you don't need updates and go through different reviewers which are applying different rules through their liking it seems.
When you do the last thing I wrote, it does not guarantee that you will pass an iOS update, for instance I have this recommend on facebook which seems to break in iOS 11.
When using a public API, if your not the first forget wasting your time to make an App for this. So API makers, make you documentation for Android, don't waste your time for iOS anymore too much.
Why are there still so many duplicate apps? Well because this rule did not exist before.
It is already very difficult to make any money from the App Store, when I switch any of my existing app to pay, no downloads, and when I switch them to free I have a lot of downloads.
Even IAPs doesn't really seem to work unless you have created the next Pokimon or something huge.
Apple is chasing young and new developers towards Android this way. I mean I like to develop for iOS as a hobby, but if I would try to change my day job with full time developing, it's the most risky thing to do because of this uncertainty. You're spending weeks of work and get wrong rejection info which makes you have a pile of work again to be rejected for something that you should have been rejected in the first place.
On top of this I did a huge effort in localization, making the interface and the app store descriptions in many languages, that was nearly as much of work as the whole app development and backend server work.
Can you imagine I would have wasted my time also in making it accessible for disabled people.
NOT AT ALL encouraging for (new) developers! I hope that Apple is not shooting in its foot here because with the new appstore ads you can have multiple apps, the one that pays the most gets the most downloads, thus this rule can go away, let economics do the job and not this arbitrariness.
Good luck to all you iOS dev that have the courage and courage to stay developing for this market.
