Understanding tremolo and octaves

So The tremolo and octave harmonicas have something I am trying to figure out. The the top row is one pitch and the note right below it is either sharp (tremolo) or an octave apart (octave). But what I didn’t realize until tonight is the hole to the right of each note is also the same pitch. So for example my octave Hering has 16 holes from left to right on the top row. But only 8 blow notes. So if it was C it would look like this

EEGGCCEEGGCCEEGG

So what is the reason on the double notes? So technically you are blowing 4 reeds per note? No wonder I run out of breath playing my tremolos and octaves. Wondering if there are any that don’t double up each reed.