Backpressure when using interval

Question

I have this RxJava2 flowable

private val pulseFlowable = Flowable
   .interval(200, TimeUnit.MILLISECONDS)
   .subscribeOn(Schedulers.computation())

and this subscriber

pulseFlowable
   .observeOn(Schedulers.computation())
   .subscribe(
      object : Subscriber<Long> {
         override fun onSubscribe(subscription: Subscription) {
            pulseSubscription = subscription
         }

         override fun onNext(long: Long?) {
            onPulse()
         }

         override fun onError(throwable: Throwable) {
            Timber.e("onError")
         }

         override fun onComplete() {
            Timber.d("onComplete")
         }
      }
   )

It produces a MissingBackPressureException, which I "sort of" understand: Since I'm subscribing and observing on the same scheduler, I initially thought maybe backpressure would not occur, but maybe that was a misconception.

When I change the flowable to

private val pulseFlowable = Flowable
   .interval(200, TimeUnit.MILLISECONDS)
   .onBackpressureLatest()
   .subscribeOn(Schedulers.computation())

I no longer get an exception, but neither is onNext called. Why is that?