no that is not true you can rewrite pcm vins as many times as you like, the only thing you can't do its write the same calibration, you can take a gm pcm and install it on any other gm vehicle as long as the connectors are the same and rewrite the vin for that vehicle do the vtd and thats it, i have done this procedures a million time rewriting vin its what its all about, the same goes for all american cars and many asian and europeans as well, the vin rewrite part of it, some pcm are vehicle specific for some other makes like ford and chrysler you can't just install one that fits it needs to be for that specific vehicle same part number.