Should I be rejecting edits like this?

No, the edit is IMO an obvious improvement.

The problem is rather that edit shouldn't have been done at all. But to me that's another story.

Once it's in the "Suggested edits" review queue, it shall reviewed solely by the quality of the edit. You are reviewing the "edit quality" - not the "question quality".

So in this case I would accept the edit but as an additional action, I would also "vote to close".

Should I be rejecting edits like this?

No, the edit is IMO an obvious improvement.

The problem is rather that edit shouldn't have been done at all. But to me that's another story.

Once it's in the "Suggested edits" review queue, it shall be reviewed solely by the quality of the edit. In other words: You are reviewing the "edit quality" - not the "question quality".

So in this case I would accept the edit but as an additional action, I would also "vote to close".