Yes, no and no.
First thing: by "hermetic" I mean "understood by people with some preliminary
knowledge about certain subject".
Precise language does not have to be hermetic, agreed. But being hermetic is
often the most efficient way to precisely communicate what you mean. Moreover,
it is generally safe to use, because it is highly unlikely that someone
without presumed knowledge will even look there.
Example. When you write statistical software, you don't explain in help what
"median" is, or how "chi-square test" is computed and how it could be used.
You expect your users to know that. The reason is simple: someone without that
knowledge wouldn't even bother to install statistical package.
It is the same case with SYD function. It is fine that it's description is not
understood by general audience, because general audience has no knowledge
about investments. In turn, general audience has no use of this function. Any
effort put into lowering entry barrier of usage of this function (e.g. by
explaining what "amount of depreciation" is) would be wasted anyway.
It all boils down to defining your target audience and purpose of help.
I, for one, think that "help" is supposed to help you in using this particular
implementation, not teach you general concept.
People who do understand general concept still need help. Let's take QUARTILE
function as example. If you know what quartile is, you still need help to tell
you what arguments can be passed to function, in what order and what are
acceptable values of them.
In fact, this is a way that most of Calc help has been written. Take a look at
ACOS help description. It will be useless if you don't know what
trigonometric, cosine and radians are.
But then, what possible use could you make of ACOS function if you don't know
what trigonometric is?
This is by no way "elitism". There are bunch of sources that can teach you
about general concept, like Wikipedia, online courses, schools, universities,
bookstores and libraries. There is no need for Calc help to duplicate that
effort.
To sum up:
- Being hermetic is fine.
- Help for particular function should be understood by people who need it. We
can safely assume they do have some preliminary knowledge.
- If help is not understood by specialists, then there is a problem.
I'm fine with anyone taking different course and making Calc help a teaching
resource. But that persone should prepare for a awful lot of work.