AppleScript works in Script Editor, but not in Terminal

Question

My objective is to create a script that sets my company logo as the icon of a webpage-shortcut-file on user Desktop.

The background is IT-management. I want to run a remote script on 100+ Macs to place a branded shortcut to my support portal on everybody's Desktop.

I found a piece of AppleScript that should change the file icon. The problem is that it works fine when I test it in Script Editor, but if I do it in Terminal, it runs, but doesn't complete the task.

Here's the code (h/t How can I change a file or folder icon using the Terminal):

#!/usr/bin/env osascript

use framework "AppKit"

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# PROPERTY DECLARATIONS:
property this : a reference to current application
property NSWorkspace : a reference to NSWorkspace of this
property NSImage : a reference to NSImage of this

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# IMPLEMENTATION:
on run
    set icon to "Users/myuser/Downloads/supporticon.png"
    set target to "Users/myuser/Desktop/supportpage.webloc"
    
    setIcon to icon for target
end run
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# HANDLERS:
to setIcon to iconPath for filePath
    set sharedWorkspace to NSWorkspace's sharedWorkspace()
    set newImage to NSImage's alloc()
    set icon to newImage's initWithContentsOfFile:iconPath
    
    set success to sharedWorkspace's setIcon:icon forFile:filePath options:0
end setIcon

Running it in Script Editor gives result: true (and the icon actually changes).

Running it in Terminal: My-MBP:~ myuser$ osascript setIcon2.scpt gives false and nothing happens. But I need for it to work in Terminal, because that's how the remote management software runs the script.

As my proficiency level in AppleScript is "monkey pushing buttons", the solution is probably something blindingly obvious. But could anyone help me to figure it out, please?