Must have been incredibly scary for you - I'm glad she seems to be ok!
I think there will be a whole host of reasons...first, if you look at the other thread (and other threads on the subject) rabbits seem to choke on all sorts of different pellets not just SS (yes there do seem to be more choke on SS, but they are the market leader so more people feed them so you would expect to see more incidences) - and all of those pellets involved in various choking incidents are different shapes and sizes. So if they change the shape from one thing to another, then rabbits who are more susceptible to choking on a different shape pellet will choke, so it doesn't actually solve anything. A&P is another one listed a number of times in the other thread, and that is totally the opposite to SS, very small and uniform, and those are fed far less frequently than SS so potentially that shape is no better or maybe even worse.
Add into that the costs of doing so as that would involve significant equipment changes, and I wouldn't have thought that the business case for doing so would stack up, especially as it looks as if changing the shape wouldn't actually solve it, it would just shift it to a different cohort of rabbits who are more likely to have problems with a different shape.