

At the very least, actual humans have an incentive not to BS you too much, because otherwise they might be held accountable. This might also be the reason why call center support workers sound less than helpful sometimes - they are unable to help you (for various technical or corporate reasons) and feel uneasy about this. A bot is probably going to tell you whatever you want to hear while sounding super polite all the time. If all of it turns out to be wrong… well, then this is your problem to deal with.
Just guessing, but the reported “90% accuracy” are probably related to questions that could be easily answered from an FAQ list. The rest is probably at least in part about issues where the company itself f*cked up in some way… Nothing wrong with answering from an FAQ in theory, but if all the other people get nicely worded BS answers (for which the company couldn’t be held accountable), that is a nightmare from every customer’s point of view.