AppleScript: alias reference is not changing after renaming a folder
I'm not quite sure why you're not getting the correct information. Running your code on my system (macOS High Sierra) returns the correct alias to the renamed folder.
This code should return the proper value for the alias value you are looking for
set folder_name to "New_Folder"
tell application "Finder" to set my_folder to ¬
(make new folder at desktop with properties {name:folder_name}) as alias
return my_folder