We have seen reports of some boarding passes with a Precheck indicator, but not granting Precheck access (I think in the UA forum, this was mentioned a couple times). But it's hard to know how much is based on the bar code encoding, and how much is random TSA "layers."

I have once received a boarding pass that indicated Precheck, but the bit was not set in the barcode (reprinted at a kiosk and it was all set).

I have also (still) received some boarding passes that don't indicate Precheck in text, but do encode it in the barcode.

So this should help take some of the confusion away...