[Turing_Machine]

"as probably most of HN knows well, keeping a codebase portable can be quite helpful in terms of plain and simple quality. Obscure bugs or bad patterns that are hard to find on one architecture can be a lot easier to identify on another."

Right. Even if they had no intent of making ARM laptops (although I suspect they probably do have that intent), the exercise of keeping the code portable between Intel and ARM would serve them in good stead even if they later went to yet a third CPU architecture.