They're more likely to now that the stuff you're getting is linked to premium currency. Imagine an exploit in overwatch that gave you free loot boxes. You'd be hella banned.
None of it is even inherently linked to premium currency.
Sure, there's the premium shop that sells like... 5 things a day? Most of that shit nobody bothers with anyway, the selections are usually terrible and not worth spending the krystals on anyway, and NRS knows that for sure.
They shouldn't ban players for taking advantage of an error in coding. Especially when it's skipping an extremely boring and unexciting grind fest.
Comparing this to Overwatch where they throw events at the players in a way to give them the incentive to spend money on Loot Boxes is an extremely poor comparison.
For one, you can actually spend money to unlock loot boxes in Overwatch. In MK11 you have to play the game and grind just to unlock one.(Let's be real, the chests in the Krypt may as well be loot boxes anyway.)