Version 3.6.4 (Archipelago)
In this case, duplicating a layer ignores the "with properties" argument. The example below duplicates a layer and at the same time gives it a new name and lock state. Those specified properties are ignored.
tell application "Pixelmator Pro"
set testDoc to make new document with properties {name:"Naming Test"}
tell testDoc
set imageLayer to make new image layer with properties {name:"Original Layer", locked:true}
duplicate imageLayer with properties {name:"Duplicate", locked:false}
end tell
end tell