Strange, i am experiencing the exact contrary behavior change !!!
For me, it now always ask to deleting the related record and i cannot choose to delete entire record anymore. But we agree, there was a change : no choice anymore with v14.
On my file, it only depends on the focus : if the focus is on the portal, a field or the entire row or an inner button, means the row will be deleted; if the focus is out of portal, it will be the entire record, obviously.
I am wondering if my post here Disabling Allow deletion of portal record IGNORED was heard and inspired this change. Now, when a field is active on the portal, that doesn't prevent delete record step to delete the related record, as it did before v14.
This change is a little bad news to me, since it mean that FMI confirmed that a scripted Delete record, even without dialog, may not delete the active record as you will generally expect, but will maybe delete a related record, and the easy workaround to systematically use a Go To Field [next] is not working anymore...
Next step would be the removal of the Delete Portal Row script step...
Having the same problem here since migrating to v14.
Scripts that have worked for years deleting a single related record using a trashcan button are now deleting the entire parent record and all children. With 30 users, this is making swiss cheese of my dataset.
Just started my search for a workaround...
In terms of a work around, there is the Delete Portal row step that should consistently delete the related record provided that you enable portal row deletion and have the focus on the right portal row at the time the script step executes.