Questions on using the SQL Server – Merge snap, where is WHEN MATCHED logic?

There are a number of ways to do this, but here is a simple example.

Basically, the Mapper creates an array of two objects with two elements for each object (rid and value). Then the JSON Splitter pulls the array apart into one document per array element.
Community 13145 - Split record_2022_08_15.slp (5.2 KB)

The example is self-contained so you can upload it to your org and validate it to see the documents as they move through the snaps for a clearer understanding of how it works.