You need to market for OP mate, I'd say it's more like, Guido and his "magic file" that gets the task of making them flat!
[seriously, I am sure they have a step to take down the shape off of ETA stock parts.] Observed closely these watches are probably loaded with small details of after-ETA detail finishes. The custom bridges, the added Swan, all things - elabore - to justify the price in the end ... "Hey, we file down the Cannon Pin! Of course our watch is worth every penny ... " It's a common practice in watchmaking to do all sorts of hand finish touches on watches - movements especially. And such a small detail does make the face of the watch look more unique - think of the imagination that thought that small detail out ...
You can take the conical top down flat [that in itself would be a task without good tooling], the other issue I would see is taking it down too much and creating your own CANNON RECESS PIN effect on a perfectly good Cannon pin! That would cause a very purple passage :shock: