I can put the question this way, with perhaps the only really pertinent example: if you take a `Shapelet` with already-defined coefficient vectors, sigma etc. and decide to change its order as far as I can see everything in the `Shapelet` is erased.  This doesn't seem transparent from the dox, and it's not a silly example you might very plausibly want to extend the order of a predefined shapelet series.   I don't think many users will necessarily know or care about the immutability of the `GSObject` classes.