I definitely don't
know that the parameter is where SpaceX wants it to be, or even more importantly where SpaceX should want it to be given the information available to SpaceX. That's why there is room for disagreement.
I do have some hints that it's probably more or less where SpaceX wants it to be, some hints that they have chosen this parameter rationally, and some faith that they aren't stupid. For instance, Elon often discusses future tests failing as acceptable, they've declined to put in place more stringent QA efforts, they're still mostly building the hardware exposed to the elements, Elon has discussed that currently their approach is building a lot of starships to iterate on the manufacturing methods and to help them make an easy to manufacture design - he has signaled fairly clearly via his tweets that actually flying the "ships" is secondary, and so on.
My prior is that the parameter is as likely to be set as too high as too low. The testing failure at this stage in development is weak evidence that it is too low, the rest of the information I've just talked about is more convincing evidence that it is an appropriate value or too high, hence I think the post I responded to is "probably wrong".
An example of where I think the level of caution was probably too low (or there were other issues, but let's pretend for a second that this is the only knob management has, as I said it is an over simplification) - the recent CST 100 orbital flight test failure. That test was intended to demonstrate they were ready to fly humans, instead they suffered a series of serious failures, failing that sort of test is pretty strong evidence that they weren't careful enough. They've indicated this type of failure was unexpected and that it will cost the company slightly under half a billion dollars, which is also pretty strong evidence that they weren't careful enough. Moreover I know that they neglected to use procedures such as end-to-end software simulation that would have reduced this risk, and that they were in fact contractually required to perform. Meanwhile I don't have any real evidence that they were careful enough with regards to that test. So starting with the same prior as above, I quickly fall to the "they probably weren't careful enough side".
> Or was at an optimal point for SpaceX in general
The optimal point is definitely not a global value for all of SpaceX. Human spaceflight programs have obviously set it very high instead of very low. As they progress from experimenting with manufacturing to flying payloads it obviously gets turned up. Etc.