This is needed because it would save contributors a lot of time and/or add useful edit info that would otherwise not be provided. It's not just an issue on Commons but also a problem on Wikidata where reverts do not have a prefilled Edit summary.

Are you sure? Both rollbacks and undo edits on Wikidata seem to work fine, edit summary-wise, AFAICT.

Maybe it was a bug then: I often (maybe always) have to write revert edit summaries manually there (two recent examples)

Your manual edit summaries seem to have been redundant. The automated edit summaries work fine, and I've attached a screenshot.

Didn't notice it says it automatically creates an edit summary – then ignore the part about Wikidata. I don't think it's good that it does not display the automated edit summary on that page somehow because when the same edit summary field is blank like it's on Wikidata in other Wikimedia projects that people may be used to then there is no edit summary at all. Separate subject.

In T372929#10079039, @Prototyperspective wrote:

Didn't notice it says it automatically creates an edit summary – then ignore the part about Wikidata. I don't think it's good that it does not display the automated edit summary on that page somehow because when the same edit summary field is blank like it's on Wikidata in other Wikimedia projects that people may be used to then there is no edit summary at all. Separate subject.

Then ignore the part about wikidata? What do you mean by that?

What do you mean by that?

This is needed because it would save contributors a lot of time and/or add useful edit info that would otherwise not be provided. It's not just an issue on Commons but also a problem on Wikidata where reverts do not have a prefilled Edit summary.