The specific difference is summarizing automatically, at scale, which is a novel technological possibility.
The previous balance of rights was created when summarizing took human time and proceeded at human pace.
Now, that's different and a new balance needs to be struck.
I believe copyright is always case-by-case. No one sues over plot summaries because they likely help sales. Summarize books or news articles with an LLM and you end up with the lawsuits we see today.