Even ignoring the fact that it is early 19th century keyboard music, not 16th century vocal music, I wouldn't analyse this as "parallel octaves". Octave doubling is very common.
In the left hand, the G and D progress to unison C's. The F resolves onto E (correctly for a dominant 7th chord).
The left hand G in the final chord is an "extra note" - but without it, the doubled third of the chord (E) in the left and right hands would sound worse.
In any case this collection is titled "Practical Exercises for Beginners" - it's not meant to be art music! For a beginner, covering up the doubled E with an extra note is a more musical solution, and easier to play, than expecting the beginner first to recognize (by analysing of the harmony, which the beginner probably hasn't studied at all yet!) that the E would need to be played softer than the other notes in the chord, and then to have a good enough keyboard technique to actually play it that way.
Note that the left hand in the final cadence is identical, except it does omit the G, and because the right hand is different, there is no doubled third.
The Schenkerian solution of "register transfer" is just counting the number of angels on pin-heads IMHO. In any case, Schenker was born 10 years after Czerny died, so any Schenkerian analysis is at best rewriting history.