It is entirely musically driven, not code driven. In fact I’m sure on some level it greatly complicates what Dorico has to do that we have to conjure up multiple notes and tie them together from a single note, so it’s certainly not driven by the code. No, it’s because a tied note is, logically speaking, a single note: that’s how we perceive it, that’s how it’s played by the performer. We can’t hear ties!
And think of all of the serious problems you have with tied notes in Sibelius: you can repitch one half of a pair of tied notes independently of the other, rendering the music nonsensical; you can add an accidental to one half of a pair of tied notes, but the other half won’t follow suit, rendering the music nonsensical; you can select both halves of a pair of tied notes and add an articulation, and that articulation will be added to both notes, rendering the music nonsensical; when inputting lyrics, you have to hit Space twice to advance past the second half of the tied note, even though in musical terms it really is a single note; similarly when repitching, you have to repitch each half of the tied note independently, and so on, and so on. Not one of these problems exists in Dorico.
I think it’s very easy to decide that something makes sense simply because it’s how you’re used to thinking about it. But I think if you reflect on this, you’ll at least be able to see the point that Dorico’s handling of tied notes comes from a musical perspective rather than a technical one, even if you want to cling to your old ways of thinking a little while longer!