One of many reasons LoL becomes popular is that it does not create much "burden of memory", Gwent is already complicated, involves lots of calculation within short rope and probably will become even harder to track cards in the future with more mechanic added.
I understand that trying hard is also a beauty of gwent but even pro gamers have to use papers to track cards in tournament, that means necessarily a tracking app is not a cheating tools, but more like something that save us writing, papers, ... This may be a good feature to make Gwent more attractive to casual players, not everyone would like to make something big.
There are more things in Gwent that makes it challenging like deck building, prediction, interaction, ... Most of the time tracking cards on your own is like "burden of memory".
So personally my opinion is tracking app should be a feature in game, but only in casual or ladder, and toggleable. Disabling it in tournament is OK.