And some other western cartoon model sheets get far more "just do what looks good, and don't do this or that because it's wrong even if it seems right" than anime. You basically just have to be so comfortable with drawing from a combination of natural skill (the large part of it) and mileage that you can pick up new rules on the fly and make changes based on what looks good while adhering to the rules of the character design and/or style.
Even for realistic observational art, you might be drawing something right in front of you and see that two things make an unpleasant tangent. You can merely stick to drawing what you see, or improve the depth and appeal of the drawing by pushing the forms to have more of an overlap. You could even be drawing a figure from life, see a value shape that's almost there but not quite, and either stick to the harsh rules of lighting and anatomy that you see in front of you, or say fuck it, this shadow shape would look better if I fudged it a bit here, and probably wind up with something that looks better even if it is "wrong."
And that's what has been done in lots of anime styles. Maybe things were started with construction, but for tons of designs, things were pushed and pulled, fudged and smudged, to wind up with something that's wrong by construction standards, but right in the sense that more people want to look at the finished result than had construction been strictly followed.