I think we don't have enough information to unambiguously answer Kaitsu's questions.
My blades are about the length he shows - but my feet are small for an adult. I have certainly at times deliberately had my blades mounted much more offset (side-to-side and to some extent front-to-back - I never really needed special directional alignment) than these are - and that was in some ways an improvement over symmetric mounting, though in the end I decided it worked better for me personally to reshape the interior of the boots than to offset the mounting positions.
Perhaps Edea is only using the dotted lines to show where to mount the blades if the skater has no special asymmetric issues, rather than being meant as a universal mounting template. Given the range of foot shapes and other anatomical differences, there is no way for there to be one best way to mount blades.
Coaches often don't have time to examine their students' boots and blades between on-ice lessons. E.g., they often schedule one student after another within the same skating session, and time is money. But if a coach is good at looking at boots and blades, it might occasionally be worth it to pay the coach to look them over before or after a skating session. Plus a lot can be told about the boots and blades by a good coach by watching the student skate and interacting with them. I guess any good coach needs to budget their lesson time between technique and equipment issues.
I am curious Supersharp - if a skater's blades show evidence of frequently repeated landings of one blade on top of the other, what do you conclude, or are you just talking about the need to deal with the nicks, which I would hope any reasonably good skate tech can do?