Flowable.observeOn and Observable.observeOn try to do as much event delivery as they can.
Add a section explaining this property to all these multi-valued observeOn overloads:

"This operator keeps emitting as many signals as it can on the given Scheduler's Worker thread, which may result in a longer than expected occupation of this thread. In other terms, it does not allow per-signal fairness in case the worker runs on a shared underlying thread. If such fairness and signal/work interleaving is preferred, use the delay operator with zero time instead."

Also link to the @see #delay(long,TimeUnit,Scheduler).