Main arguments are a matter of interpretation, so your second sentence opposes, rather than supporting, the first.
Summarizing is interpretation, since it is relaying the important points of the source, and determining what is important is a matter of interpretation.
Nope. Selecting which main argument to repeat is a matter of interpretation. But once you've selected it, repeating it requires little interpretation. Adding your own commentary requires interpretation in both selection and writing.
We might have different definitions of the word "interpret". According to Google, interpret: 1) explain the meaning of (information, words, or actions). 2) understand (an action, mood, or way of behaving) as having a particular meaning or significance.