SDK how to stack images using catalog:addPhoto( filePath, photo, 'above')

While importing photos from disk I'm struggling to stack these photos with existing photos in the Lightroom catalog.

My use case:

In my Lightroom catalog I have 2 images
On my disk I have 2 other images, noy yet loaded into Lightroom.
Their file name makes it clear which image on disk belongs to which image in the database

I'm using:

catalog:addPhoto( filePath, photo, 'above')

What works well?

The images are loaded into Lightroom.

What works not?

They are not stacked.

Question: what am I missing?

Steps to reproduce

1. See the attached images
2. Import the two photos without "_nbg" into Lightroom
3. Put the other two, without "_nbg" in the file name, into some directory.
4. Change in my sample code below my directory name with the directory name you used above.

I downloaded the images from Unsplash.com

local LrApplication = import "LrApplication"
local LrDialogs = import "LrDialogs"
local LrFileUtils = import "LrFileUtils"
local LrFunctionContext = import "LrFunctionContext"
local LrPathUtils = import "LrPathUtils"

local logFilename = "StackPhotos"
local myLogger = import 'LrLogger'( logFilename )
myLogger:enable( "logfile" )

local catalog = LrApplication.activeCatalog()

local function findByName(filename)
	local foundPhoto = catalog:findPhotos {
		searchDesc = {
			criteria = "filename",
			operation = "all",
			value = LrPathUtils.replaceExtension(filename, "jpg"),
			value2 = "",
		}
	} 

	return foundPhoto
end

local function main()
	myLogger:info("Main: start")

	--Import both photos WITH background in Lightroom: everyday_matters-closedEyes.jpg and Reinaldo Kevin.jpg
	--Put in the directory of your chosing the 2 images without background: everyday_matters-closedEyes_nbg.png and Reinaldo Kevin_nbg.png
	-- BTW _nbg stands for no background
	local destinationPath = LrPathUtils.standardizePath("D:\\Temp\\Lightroom Burned Exports\\output")
	myLogger:info("destinationPath", destinationPath)

	--	Prepare database for adding photos
	catalog:withWriteAccessDo ("Stack", function ()

			--			Loop the folder with the image with no background
			for filePath in LrFileUtils.directoryEntries( destinationPath ) do

				--				Determine the file name of the original photo by removing the "_nbg"
				local leafName = LrPathUtils.leafName(filePath:gsub("_nbg", ""))

				local photo = findByName(leafName)[1]
				if (photo) then
					myLogger:info("Image found", leafName, photo, photo:getFormattedMetadata("fileName"))
					catalog:addPhoto( filePath, photo, 'above')
				else
					myLogger:info("Image NOT found", leafName)
				end
			end
		end)

	LrDialogs.message("Stacking photos", "Finished stacking photos")
end

LrFunctionContext.postAsyncTaskWithContext ("Stack photos", function( context )
		LrDialogs.attachErrorDialogToFunctionContext( context )

		main()

	end)

The log file

05/20/2024 16:18:37 INFO	Main: start 
05/20/2024 16:18:37 INFO	destinationPath 	 D:\Temp\Lightroom Burned Exports\output 
05/20/2024 16:18:37 INFO	Image found 	 everyday_matters.png 	 LrPhoto( id "126" ) 	 everyday_matters.jpg 
05/20/2024 16:18:39 INFO	Image found 	 Reinaldo Kevin.png 	 LrPhoto( id "121" ) 	 Reinaldo Kevin.jpg