A couple of thoughts ...

1. In my experience, the pool of resources that can build complex integrations using the Health Connect GUI is an order of magnitude larger than those that can do the same in pure ObjectScript. The rarer the resource, the more it costs.
2. I've also found that some of those that have used ObjectScript as a method to enhance/alter the behavior of production components have implemented "private" methods or relied on undocumented behavior that has the potential to change or become deprecated, requiring extensive testing and possibly re-coding when upgrading.

You can do this by creating a collection object in a code block, and iterate over the comma-separated string to populate it:

 Set tArray = ##class(%ArrayOfDataTypes).%New()
 For i = 1:1:$LENGTH(LookupVal,",")
 {
     Do tArray.SetAt($PIECE(LookupVal,",",i),i)
 }

You can now iterate over the collection variable in the for each action:

Seems like the operation isn't working as it should; you may want to take this up with the WRC.