RxJava-Android-Samples | Learning RxJava for Android by example | Reactive Programming library

combineLatest() must have all values for starting emitting something, as by definition the combiner function gets n values that emitted from n sources.

When RxBInding wraps TextView events with RxTextView, it emits an initial value (contents of the TextView) when subscribed, so without the skip(1), you will have your desired logic, the thing is the validation logic in this sample do not expect that, and display error for empty values (by the !isEmpty(newXXX) checks).
My hunch based on the explicit skip(1) transformation is that in this example this is the desired behavior - meaning just when all fields has been entered we need to display errors.

In your case if you want to implement your logic, you need to skip empty values from displaying errors while still emit false at the end as the whole input is not yet valid, then - with any change at any fields independent of the others, while not empty you will the errors .