As to why their methodology is important this isn’t the Falcon 9 this is a new launch system which is likely going to have multiple failures before it’s own streak can begin.
So sure, we can reasonably assume that Starship will get to a state of reliability similar to current Falcon rocket, eventually. We can’t assume the first few commercial Starship launches are going to even approach that level of reliability. And in fact the best point of comparison may be the early days of Falcon 9.
Speaking of methodology, it's incorrect to relate a development test result to reliability or risk. Source is my personal experience doing reliability calculations for a NASA rocket component and working with the statisticians incorporate my numbers into their risk model.
So sure, we can reasonably assume that Starship will get to a state of reliability similar to current Falcon rocket, eventually. We can’t assume the first few commercial Starship launches are going to even approach that level of reliability. And in fact the best point of comparison may be the early days of Falcon 9.