Mark Gurman, Bloomberg:

The most direct benefit of the Marzipan project will be to make life easier for the millions of developers who write software for Apple’s devices. For example, later this year Netflix Inc. would be able to more easily offer a Mac app for watching video by converting its iPad app. By 2021, Twitter Inc., which has mostly abandoned the Mac, could publish a single app for all Apple customers.

And:

Despite the app merger plan, Apple has said it won’t combine iOS and macOS into a single operating system.

This latest bit on Marzipan is all according to “people familiar with the plan”.

The ability to create a single code base, with interface adjustments for all the various screen sizes (which developers do now), does seem a boon for developers.

It’ll be interesting to see how Apple accommodates the variety of input devices and the difference in targeting sizes (difference between touch with a fat finger, and precise clicks via a mouse).