I've resolved my issue with the following solution:
Create an Approval action – call this “Review”
Create another Approval action directly below, for the delegation – call this “Delegated Review”
Create an Update action underneath to update your list based on the “Delegated Review” outcome – call this “Update Post Delegated Review”
Create a parallel branch (alongside the “Delegated Review” action) and add an Update action to update your list based on the “Review” – call this “Update Post Review”
Create an action (in my example a send e-mail action) to bring the two branches back together – call this “Outcome”

Go back and change settings for the “Review” action to time out after PT2M (2 minutes – for testing) or PT48H (48 hours for real).

“Configure run after” for the “Delegated Review” to only run if the “Review” has timed out

“Configure run after” for the “Outcome” to run if the “Review” OR the “Delegated Review” have been skipped, OR either have been successful.

All other settings in all other actions are left as their default.
If the “Review” is successful (i.e. if the recipient reacts within the timeframe) the “Update Post Review” will be called and the “Delegated Review” branch, including the update beneath, will be ignored (skipped).
If the “Review” times out (i.e. if the recipient does not react within the timeframe) the “Delegated Review” branch, including the update beneath, will be called.
The “Outcome” action ties the two branches together.
Hope that helps some people out there. Let me know if it does!