I assumed the same as you're saying, but it just doesn't. If I run the below test script I get error 32 "The process cannot access the file because it is being used by another process.". Even withe the redim and a 15 second sleep.

 Code:
$System = CreateObject("Kixtart.Form")

if $System.Version <> "2.47.5.1"
   $System = 0
   ReDim $System
   Sleep 15
   $oldkf = ReadValue("HKEY_CLASSES_ROOT\CLSID\"+ReadValue("HKEY_CLASSES_ROOT\Kixtart.System\CLSID","")+"\InprocServer32","")
   Copy @ScriptDir+"\kixforms.dll" $oldkf
   ? @Error
   ? @SError
endif

get $