KTN didn't show up on my boarding pass although the words precheck or the little precheck tick logo showed up on the paper boarding passes. In addition, they appeared on the mobile boarding passes. This has been consistent across all my domestic flights in the US since getting Global Entry, including flights with both United and with AA this weekend (the latter being a reward booking on AA using BA Avios).
It is also interesting that the precheck logo also appears on AA boarding passes with departing from DUB. I thought that was odd as there is no precheck benefit there, but it still appeared nonetheless. Presumably just an error perhaps relating to DUB having preclearance.
Also, my wife has Global Entry and we used her precheck benefit this weekend. This is despite her name with Global Entry/TSA precheck being in her old name. We hadn't expected to use it given she has changed her name since getting married but the boarding pass still showed 'precheck' when we printed it out. We went through without issue even though her passport shows her new name (which fyi matched her boarding pass). Perhaps, it is because her surname is a hyphenation of her old surname and her new surname. Either way, we'll head to a Global Entry enrollment centre at some point before her next flights in order to get the surname updated.
Simon.