I see what you're saying, but the post above seems to indicate that understanding those models SHOULD be important to you if your job is to run those models and explain results and make corporate decisions based off your forecasts. You shouldn't be just passing data through and thinking that it's not your job to actually understand things. The subtlety matters a lot as the software hitting some edge case could completely skew the results. There is a vague line drawn somewhere that tells you what is necessary to learn and what is superfluous. Finding the line isn't easy, but those that label too much as superfluous will likely get more erroneous results and that is a problem.
With regards to your API statement, I'm just as guilty regarding reading the code, but I do run some manual tests to ensure that my script calling the database actually does what I think it should. Is that good enough? Who knows :)