“compare A with B”

Hello, everyone,

While working as a research fellow at Harvard, B. F. Skinner carried out a series of experiments on rats, using an invention that later became known as a “Skinner box.” A rat was placed in one of these boxes, which had a special bar fitted on the inside. Every time the rat pressed this bar, it was presented with food. The rate of bar-pressing was automatically recorded. Initially, the rat might press the bar accidentally, or simply out of curiosity, and as a consequence receive some food. Over time, the rat learned that food appeared whenever the bar was pressed, and began to press it purposefully in order to be fed. Comparing results from rats the “positive reinforcement” of food for their bar-pressing behavior with those that were not, or were presented with food at different rates, it became clear that when food appeared as a consequence of the rat’s actions, this influenced its future behavior.

*source;

https://books.google.co.kr/books?id=qZKbBgAAQBAJ&pg=PT151&lpg=PT151&dq=%22using+an+invention+that+later+became+known+as+a+%E2%80%9CSkinner+box.%E2%80%9D+A+rat+was+placed+in+one+of+these+boxes%22&source=bl&ots=-Pcsj-NB61&sig=ACfU3U25l3vL-h1imhACTM_H60IVLcx8BA&hl=ko&sa=X&ved=2ahUKEwi7lu-5goDxAhUgyYsBHRA1DQsQ6AEwAnoECAIQAw#v=onepage&q=%22using%20an%20invention%20that%20later%20became%20known%20as%20a%20%E2%80%9CSkinner%20box.%E2%80%9D%20A%20rat%20was%20placed%20in%20one%20of%20these%20boxes%22&f=false

I have a question – why didn’t the writer write, “ ~ with those(=results) from those(=rats) that were not ~ ” in above underlined part? I understand in English the comparison pattern needs the same comparing noun strictly by using the proper pronoun as per the sentence;

* The population of Paris is bigger than that of New York or London.

Maybe, do the writers sometimes leave out the repeating noun - “results from” for simple structure in such a pattern – “compare A with B”?

Would hope to hear,