I'm actually glad they're taking the time on trials.
We're basically still at a very early stage of their ascension, this stage is usually gone and forgotten very fast in other similar series.
Here, instead, they expand it a lot, showing all the behind the scenes of every trials and schemes, I must say that I enjoy this a lot more !
The instant that guy with the eye couldn't discern the cards, I was sure the answer was that they all were real. If the trick is like the loaf that never ends, he could very well have an artifact that spits endless copies of something (with restriction like time, not consumable, by value, etc). Anyway, if they were so confident to begin with, it exactly was because it's definitely not an illusion but certainly a trick.