Yes but the problem with "never been shown" is how it's often used to "take advantage" of people's interpretation like what you list above. For example droppin

Yes but the problem with "never been shown" is how it's often used to "take advantage" of people's interpretation like what you list above. For example dropping a 27.4 kg ball on someone's head has never been shown to cause injury. We've dropped a 26.3 and a 29.5, but we've never studied dropping 27.4 kg - and as a result, "dropping a 27.4 kg ball on someone's head has never been shown to cause injury". Frequently "never been shown" its used as a weasely way of saying "we've never looked at", or "we don't know if"