When doing an A/B which is preferable for larger than 100g extractions it is essential because it converts the DMT to DMT-acetate. This is resistant to high temperatures. If there was no acid the ph normally sits around 6 or 7 but I know there have been people who have extracted with no acid and have had some results.
Still it really is the heat that forces the dmt out of the plant matter and acid helps too. Just think u have gastric acid (hydrochloric acid) in ur stomach to break down foods... likewise we use hcl aswell as vinegar.
Leave it to that way the teks describe, this is beyond a decade worth of trail and error. I wish though I could just magically take out all the dmt from the bark no hassles with my super powers telekenesis but no, just a human