I'm working with a developer right now who created their first big offering on IOS back 5 years or more ago. Half of the coders who started that project are no longer with them, and this year they started a cross platform project to turn that first app suite into something they could sell to a larger market (this is a medical practice product).
They first started with Android, and now have added native Mac and Windows support.
They have multiple departments, each responsible for different parts of the suite, and then specialty groups that handle the different platforms. And in the middle is a team that hooks it all together.
Some of this takes place in the cloud, but the apps each have to have a similar look and feel and communicate with the cloud the same way.
Having spent hours on the phone talking with their tech support and their developers - I can see it is a huge undertaking to make it all work.
Mind you, MF is not that complex by any means, but still, they had to do a lot of the same things to get their app to work across these different platforms.... Maybe not a "complete re-write", but I bet it feels like it.
I dunno, I've only dabbled in these types of apps, I'll stick to variants of C thank you very much =)
Good luck to them - I'm waiting - pseudo-patiently.... hehe