Hi Josh,
Let me give an example to illustrate my point why the web interface is limiting.
Imagine an adgroup with 2 Ads. Both Ads were created as mobile preferred Ads (i.e. the mobile preferred option is checked). In this case (and assuming the mobile bid adjustment is anything but -100%), these 2 Ads will run on all devices (both desktop and mobile devices) i.e. they will behave as if they were both created without the mobile preferred flag checked.
Now, since they will run on all devices, I'd like to define both the finalUrl and the mobileFinalUrl. However, as you know, creating mobile preferred Ads via the web interface does not allow you to define the mobileFinalUrl. So I now have Ads that run on desktop devices using finalUrl and on mobile devices using also the finalUrl.
The question is why there is a discrepancy in how the web interface works? If it allows us to define finalUrl and mobileFinalUrl for deskptop Ads, why doesn't it let us do the same for mobile preferred Ads? The end result is not the same in this scenario.
Oliver