Your best bet here is probably to contact the editor requesting clarification on what’s being requested before you put in a lot of work. Perhaps something along these lines:
Dear $EDITOR, we welcome the reviewers’ feedback and would like to obtain clarification on the recommended changes. Reviewer 1 has suggested $THING1 but the summary proposes $THING2, which is different because of $REASONS and would be a broader change. Could you please clarify whether these broader changes are required, or if it will be sufficient for us to address $THING1?
Or, if you really don't want to do $THING2:
Dear $EDITOR, we welcome the reviewers’ feedback and would like to obtain clarification on the recommended changes. Reviewer 1 has suggested $THING1 but the summary proposes $THING2, which is different because of $REASONS. It is not feasible for us to do $THING2 because of the amount of extra time this would involve. Would it be acceptable for us to submit a revision that addresses $THING1 without the broader changes implied by $THING2?