If it is actually verified (as opposed to just hypothesized) that the angle of the tibia is a) inherited and b)responsible for knee problems (fortunately we haven’t had knee problems here, so I’m not completely familiar with the literature on that) then it would be hoped people would try to avoid producing it. It’s not that easy though - you’d need a way of screening for it (I would think x-rays would work) but also a way of determining at what point it is a problem. I’m guessing there is a wide variety of tibia angles so you’d need some way of saying “this one is a problem” and “this one is ok”, which is essentially what they try to do with hips using either the OFA grading system (subjective) and the PennHip system (more objective but you still need to figure out what numbers are good/bad). The problem with determining that, is it is most likely a combination of tibia angle, other structural issues, and tons of environmental factors so to isolate the exact effects of the bone structure wouldn’t be easy.
I think that if in the future, a system is developed that can grade knees, then people would absolutely try to avoid producing cruciate-tear prone dogs. It’s a long way off though.