interesting to see that these tests are rolling out. These are quite new (at least at Bain, don't know about Accenture), so I think even for the companies themselves it is still a testing phase where they are learning how useful and accurate these tests can be. Although they do attempt to map out psychological traits, there is of course not a 'standard model' of who you should be. Companies using those are probably themselves trying to understand what are the traits that can predict a good consultant.
Now some types of questions in there do score you on e.g. how good your memory or reactivity is (like some of those computer games that give you your 'brain age'). You can probably become better at them by playing those kind of game/tests, but in my opinion that will not be the best use of your time. If you want to 'game' part of the process, probably best to practice cases and quantitative tests ;)
So bottom line, and as you mention, it's not really something where you'll be right or wrong, and moreover it's not something that will really count vs. interviews and quant tests. Hope this helps a bit!