Whether Maier was bold (or not) making photographs of people, well, that's conjecture. And, in the end, without other more definite information, likely says something more about the person making that assessment.
Speaking only for myself... When making photographs of strangers on the street, whether candid or not, for me it's more about being open, friendly, and honest in the manner in which I engage subjects. It's not about being bold at all.
At the other end of the spectrum, people on the street are very perceptive, especially in spotting odd behavior. Being sneaky, using deceptive methods to get a photo (looking in one direction while shooting in another, pretending to fiddle with your camera while sneaking a shot, making hip shots, etc) is often detected and creates awkward situations.
My *guess* is VM was comfortable and easy-going around people with her camera and that came across to others as non-threatening and not a big deal.