Windows 10 build 17735.1000 is an interim version as Microsoft continues to work to eliminate as many problems as they can before general release.
Microsoft also changed the naming from redstone 6 for 19H1 for the skip ahead to the following release. This suggests Microsoft has more work on the following version to do than expected so the Q1 release date seems to be pushed back.
The phone app now works properly which can now be crossed off the list of issues.
Fixed is a problem with Mixed Reality and spoken commands like “flashlight on” would not work etc.
Also fixed is ctrl-0 which now properly resets the view to 100% as expected.
A few more issues with the narrator are in this build as well. Microsoft has worked very hard on this component as they want accessibility in Windows 10 be be extremely strong.