if they believe there is no cheating in this kind of assessment they must unbelievable stupid or they are smart.
Let's believe that they are smart.
This means that they have build in some ways of detection. So if you start using calculators or have 3 buddies helping you at the same time they must find out. Easy in the second round were you will do the same kind of test but without aid. (but at least you made it to the second round!)
In other cases they had a couple of easyjet pilots doing the tests making up a demographic of the kind of pilot they want. Somebody knows about this profiling?
At the end better to be yourself than to smart (or to stupid)?