There is a difference between shellac and CA glue, and a French Polish and a Friction Polish.
French Polish is different because it is using shellac which behaves different from CA glue, and the oil and shellac are never mixed into an emulsion. The shellac and the oil are placed on the rubber alongside of each other without mixing them together, and the rubber hits the wood with the shellac in the lead so it goes down on the surface and the oil goes on over the top. The oil is always ON top of the shellac, not IN the shellac.
We use the same oil and shellac with a Friction Polish, but it is mixed into an emulsion in a bottle. That means the oil has to come out of an emulsion and rise to the top of shellac film. Otherwise it is trapped in the finish and we get the soft and poor finish that friction polish has a reputation for being.
The shellac friction polish finish can be as good as the French Polish if we get the emulsion really hot (friction) on the wood so the oil is boiled to the surface and the shellac is melted onto the surface in a continuous film. This is difficult to do because that means about 160F temperature, and that is way hotter than most wood turners are willing to cope with and burned fingers.
We can also get a better friction polish film if it is applied just as I describe the CA/BLO finish. Put on a wet coat of shellac, and follow that with a light coat of oil. We can also put both on the same piece of cloth, but alongside of each other, and apply them to the rotating pen with the shellac leading the oil just as with the French Polish rubber. Either way, the oil is always on top of the shellac, just as it is with the French Polish, and the shellac will be a harder and more durable finish just as it was with the French Polish.
Nobody ever does this because we love our Friction Polishes in a bottle because they are fast and easy to use. The price we pay for the speed and convenience is a shellac finish that isn't all that it could be. A shellac Friction Polish emulsion will always be softer than one where the oil was layered on top of the shellac as in a French Polish. The pen finish that kept the shellac and oil separated will have a hardness similar to that of a nitrocellulose lacquer.