What you are referring to is a statement I frequently make -- 100% coverage is the goal. It's an asymptotic goal, but it's still the goal. No lesser goal makes any sense.
I am not sure that 100% can be called an asymptotic goal, given that you cannot even get close, for real systems. Once you recognize this, you can start having a realistic discussion about what you actually will be able to test for, how best to allocate your limited resources, and what other steps you might take to mitigate the consequences of this unfortunate fact. It means that methodologies bassed on extensive testing must justify this use. An additional benefit is that we might be able to discuss what we can do to improve software development without the sort of dogmatic non-sequitur that I mentioned in my first paragraph.
What is a goal then? A maximum? A desirable attribute?
I'd argue a fixed percentage target of any kind doesn't make sense, much like measuring productivity by lines of code.