Comparison turns revision history into evidence: additions, removals and changed passages become visible without opening two files side by side.
Memory is poor at tracking rewrites
After several editing passes you remember the intention of the rewrite more clearly than the exact changes. A comparison answers concrete questions: what disappeared, what grew, what moved, and whether the new draft solved the original problem.
Comparison is editorial, not only technical
Did the shorter opening also remove needed context? Did the AI rewrite flatten a distinctive phrase? Did the editor pass remove repetition but weaken the rhythm? A diff is useful because it makes those editorial trade-offs inspectable.
When comparison is unnecessary
If you fixed three typos, you probably do not need a comparison. It becomes valuable when the revision changed meaning, structure, tone or a substantial amount of text.
Why text versions? · Why lock a version? · Why AI + versions?