Well… not exactly. As in many other routes the code is a bit more nuanced than that and not only binary; yeah, the player can chose for Ian to go full cuck (ian_cuck = 2) and for Lena to deny and humiliate him at every occasion (after and before the famous footjob scene), or to kill that route once started (ian_cuck = 0) OR you can chose to remain in that path but to a lesser degree (ian_cuck = 1) and for Lena not to deny him sex (again, also a choice, not mandatory).This is extremely evident with how the "ian_cuck" path flows; it's binary, once you're on it, you can get off it by answering "nah I dont wanna hear those stories of your professor" during the footjob scene (iirc there are some other places to get off it), point is, it's either sexless ian with humiliation, or full relationship with fucking, and Lena keeps any indiscretions secret. Again, it's crystal clear what eva likes to anyone who's read the code at length.
This way Ian -who in that route is undoubtedly traumatized by his experience with Gillian and dabbling a bit (unconsciously or not) with the cuck fetish- is still getting plenty of sex from Lena (last time as late as in the epilogue of chapter 11 after she comes back from the club, but also many times before in chapters 10 and 11), and even more than that: in that route is also possible to play a Lena that has not cheated AT ALL, not even masturbated to Seymour, and simply (at least for now) enjoys teasing Ian now and then. That’s because hooking up with Axel in chapter 9 isn’t the only gateway to open the cuck route later in chapter 10.
TLDR: Is possible to be in the cuck route without a sexless and humiliated Ian (and not talking about handjobs, footjobs and blowjobs only, but sex with Lena squirting and all the fireworks) and even with a perfectly faithful, as of now, Lena. It all depends on the player’s choices.