It's fair to point out that there are other scenarios where cheating can happen. But if you take that train of thought further, there are also infinite ways the romantic, cheating, cuckold, reluctant, or whatever other paths have you, can play out.
Basically, what's being asked for is a cheating route that doesn't have asshole Ethan, in whatever form that takes. Maybe it could still happen if you have an initial Ethan reluctant/romantic route and Nat decides to be faithful... at first. It's all about the character development, after all, and getting Nat to that situation where her defenses fall.
But, it's also a practical matter, and a lot of the scenes so far (apart from the car), are variations on each other, so it would take more time and energy to create this scenario (which probably won't be transferable to other routes) and then find a way to link it into the Ethan oblivious/reluctant NTR/cuck paths.
Basically, what's being asked for is a cheating route that doesn't have asshole Ethan, in whatever form that takes. Maybe it could still happen if you have an initial Ethan reluctant/romantic route and Nat decides to be faithful... at first. It's all about the character development, after all, and getting Nat to that situation where her defenses fall.
But, it's also a practical matter, and a lot of the scenes so far (apart from the car), are variations on each other, so it would take more time and energy to create this scenario (which probably won't be transferable to other routes) and then find a way to link it into the Ethan oblivious/reluctant NTR/cuck paths.