I don't think so. Nor is simply 'accurate' quite right. Unerring adds the element of time/repetition. As Welsh Dragon says,
To be unerring means not to 'err' - ie, get it wrong - not once, but repeatedly, consistently, reliably.
Thanks, you've worded it better than I ever could. The exact situation we work in and the expectation placed on us.
Yes humans do make mistakes but the level of consequence is the thing. Same as not looking where I'm going walking across my front room (stubbed toe and annoyed dog) or not looking where I'm going pulling my bike out into fast moving traffic (dead).
My level of concentration and accuracy in the performing the latter is far more crucial and significant to be right every time, as it is in the wider JD extract of unerring accuracy that would give away more of what I do than I wish to.
Thanks for the replies all, I'm glad that its not just me getting what it means.