While I've only ever handled about 3 very briefly, I've seen a bunch of photos. Just like Busetto corners which Prescott used as well, I think it's one of those high risk, high reward type things. We rarely remember the people who make copies I guess? They essentially started out bass making in America with limited contact with the tradition and came up with some pretty decent basses, so I'm not going to knock them for adding some sort of visual signature to their bass.
I've gone back and forth over the years on both features and whether I personally like them or not, but they are both a feature of a lot of Prescotts, and one that has been changed on a lot of them over the years too. Many of those basses also started off quite large and were altered to be closer to modern dimensions, so I could see how some of the other features might not look right when the outline may have been changed. That was a far more common practice than we like to talk about, where a lot of really fantastic but exceptionally large instruments were significantly altered.
Going back to the original question: Prescott made a few different models. I do not believe all of them originally had attached f's, but many did. Many of them have been cut over time, and many of them have also been restored over time. I wouldn't use that as the defining "is this or is this not a Prescott?" feature because of that. If you're interested in buying an instrument like that, I would ask for some documentation and see if they have a certificate or appraisal from a reputable shop, (they would have to get one to insure it) and I would also not find it unreasonable to take it to a reputable shop/maker/repair person of your choosing to make sure it's on the up and up. If the person selling it just retired from a major orchestra and wants to cash in his nest egg, that's different from a random internet ad, but I'd still want to verify for Prescott amounts of money.