Answer: A related question that you've probably already seen was Question 84. But yours is a little different: You are referring to what are intended to be two independent voices, not a mere orchestration effect. And so yes, a perfect octave going to a unison is basically the same thing as parallel octaves. The same applies to fifths: merely switching the octaves of a parallel fifth doesn't remove the parallel: you still have two voices separated by a perfect interval and moving to another perfect interval, still detracting from the desired sensation of independence.

Kitson (The Art of Counterpoint, p. 21) states the rule this way:

"Consecutive octaves and fifths are forbidden, whether by similar or contrary motion."