I assume that with "it" you are also referring to how easy it is for developers to port apps. I place little faith in those claims.
People not involved in the software industry tend to greatly overestimate the importance of how a UI looks in terms of how that impacts porting costs. Compared to the costs incurred by each OS having completely different libraries, frameworks, and (less importantly) using different programming languages, the impact of a more similar looking UI is limited. Consider that even with a similar UI, the instructions that draw those similar UI's to their screens are still completely different. What we're talking about here is solely conceptual similarity, not technical similarity. That's not nothing, but for something as simple as an app, conceptual similarity isn't that big of a deal either. How much of a difference do you expect that to make? How long do you think it would take for someone who made, say, Tapatalk for Android, to come up with the corresponding design for WP? I'd say most people on this website could do that rather quickly. That's the difference we're talking about. Not more.
IMHO the view that this would make a substantial difference can only be maintained through ignorance.
There is an entirely different angle which might make more sense. We've heard about MS potentially attempting to provide a way for developers to develop an app but once, with the ability for that single app to run unmodified on all three platforms. That is not called porting, nor would that directly affect any of the Android apps that already exist, but having a very similar UI is probably the only way to get that to work effectively. If MS is in fact working on that ability, then you can bet your bottom dollar that's what's behind these UI changes. Not porting costs like some are speculating.
And one last thing. I work in the software industry and have over the last few months talked with multiple CTO's who's companies don't provide apps for WP. They don't all have the same reasons for not supporting WP, but none of them cited porting costs as a reason either.
The "app economy" is highly unequal, like the real economy. According to stats from Vision Mobile, 85% of the app developers (interested in revenues) make less than $1000 of monthly revenue, and there are also many non-profit and non-comercial apps.
So, in many cases a 10% or 20% of cost savings could make the difference to make viable a WP project, probably not for a big company, however, niche apps or small local apps are also important in the smartphone experience.
Apps also vary widely in the complexity of the code vs. complexity of the UI. Some developers invest a lot of time and resources in the UI, a big part of that investment could be lost if a different UI is needed for WP.
Designing an UI is as easy as writing code, anyone can do It, but most of us would do an awful job. I'm not a dev and I can write awful code that could make cry a good developer.
As other guys said, a closer equivalence of the UI elements with Android could make possible automated tools that to generate the XAML code. Java and C# are quite similar, It's easy to automate the translation of code. The problem are the APIs, but maybe some adapters could be used to provide some of the Android APIs in C#.
Of course It's impossible to generate a working app ready to use, but part of the work could be automated, and links to documentation could be inserted as reference for a manual translation, or to improve the automated code. The objective is to reduce the cost of development for small projects.
There are other tools like Appcelerator, (I don't know if they're still around), which provide a common API to develop NATIVE apps in a neutral language, javascript in the case of Appcelerator. WP is always a problem, the lowest common denominator is too low if you add Metro weirdness to a common API.
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CTO told me this or that It's not a good argument. At the end economic decisions can be simplified to Net Present Value and Opportunity cost, or an alternative analytical framework with those elements.