On the 13th, Josei Jishin reported that they had confirmed with NHK Kouhaku Uta Gassen insiders that Ado‘s appearance as One Piece character Uta was a pre-recorded segment, as opposed to actually performing on stage live as viewers are used to.
— sakamiti46 (@46Sakamiti46) January 1, 2023
When Kouhaku was asked for a response as to why it had a LIVE tag, the response from NHK was that while the singing was pre-recorded, the audience and dancers were not.
Much of the reactions from the public to this news was mixed. Some people asked why this was becoming news now, as it was quite apparent when they were watching the show that it was highly likely the singing was all pre-recorded as it sounded too close to the original release. Others pointed out that there should be something to separate a live performance from a music video or CD, and that live singing is certainly something they had looked forward to.
Source: Yahoo JP