It's rare for information about ticket acceptance to be provided on screens or announcements though. It's usually only provided on National Rail Enquiries's disruption pages, or on the TOC's website or social media. The only other way it's common for the information to be provided is directly by the staff.The embarrassment was unnecessary - i.e. it seems they forgot to announce it. That would perhaps justify an apology for the failure to announce it.
Having read back, good customer service would, as the OP requested a reservation, have been to honour that reservation as it was the company's error, of course. However, that doesn't make the principle of TPE ticket acceptance being in SP wrong.