I think it’s because the Decca label book by Paul Pelletier lists his debut single as issued on 78 - the 7” is on 45cat here: https://www.45cat.com/record/f11185uk

However, I can’t find any images of the 78 online. That’s probably why I didn’t add it here. A user of Rate Your Music lists it in his collection. He’s on this site too, so I’ve sent him a message. It’s possible that it could have been issued on 78 and that it hasn’t been sold online in recent years. It wasn’t a hit. Perhaps some of those late 78s haven’t survived at all.

Update: the user only has the 45. So the 78 was apparently issued, but its existence isn’t confirmed.