I agree with Wullie on this one. Dogs can become 'test wise', which I presume Bryn means by 'situational', but the steadiness wasn't reliable before entering the tests. I think we've been down this road before with Bryn but there are no grey areas where steadiness is concerned - a dog is steady or it isn't. When you start talking in degrees of steadiness then you should realise that you haven't 'steadied' the dog. A 'steady' dog is a dog that is 'steady'. Period. It can never, by definition, be 'much steadier' or 'quite steady' or 'almost steady', because that only proves that it is not steady. And if you are simply 'holding' it from breaking then it isn't yet 'steady'. Steadiness is all in the mind of the dog, & handler. A dog that has been trained to be steady produces a reliable behaviour, under all conditions, so train for that behaviour - no fidgeting, no itching to go, no hair trigger responses, no 'secrets of training', just boring old repetitive training until you've got the behaviour nailed . I know that time is often short for you but you can do all the groundwork for this sort of stuff around the house anytime that you have a few moments to spare. Until you get the 'steadiness' problem fixed at 'home', while ever you keep putting this dog into a working test situation for a bit of fun or (bad) experience then all you are doing is effectively training for unsteadiness in those situations.
I do agree with Judy that dogs can & do learn to discriminate through experience but as Wullie points out, we are talking about dummies here & a youngish dog that is in the process of being trained, not an experienced dog in the process of being untrained.

And dogs do settle into their trained habits as they mature but you have to maintain the training of wanted behaviours for them to get that far. They can just as easily settle into unwanted behaviours if your training slips.
Naj