My understanding is that, although the data on the barcode itself is not encrypted, each barcode has a signature. Change a data element without changing the signature and the BP will not work for PreCheck. It will beep three times, but with a red light. This means PreCheck eligible, but an invalid signature. In that case, you don't get PreCheck.

So it isn't going to work unless people figure out how to create a good signature, and that probably isn't that easy-- certainly not as easy as just changing a data element.

So PreCheck doesn't need to be suspended (for this reason, anyway).