Completely copying the project across is still synchronization at the project level (the minimum level necessary for the fidelity of a Scrivener project) even if the data copied is not as granular as you would like. It’s merely a brute-force synchronization.
You’re confusing the goal with the mechanism(s) required to achieve that goal.
All synchronization is, at the end of the day, is “Does the object in location A match the object in location B?” That’s the goal.
The mechanisms used by sync services such as Dropbox, iCloud, OneDrive, etc. tend to be ones that try to minimize the amount of data sent over the wire by only copying what has changed. That’s a worthy design goal for modern infrastructure – keep the bits sent over limited data connections to the minimum possible. But that is not an absolute REQUIREMENT for a synchronization solution. These services use the file as the most granular object they look at – if you change one byte in the file, the whole file gets copied. Synchronization services used for other purposes can go even more granular – block level for disk file systems, even byte-level for really exotic stuff – but for Scrivener, file level is adequate (as long as you get all the files in the project).
However, not all sync services are created equal. iTunes offers a rudimentary sync service, but it doesn’t offer file-level granularity. It still gets the project synchronized between desktop and mobile device, however. And L&L has spent a lot of time explaining the technical reasons why Dropbox is the only alternative to iTunes in Scrivener – the other services work in such a fashion that they are far more likely to cause corruption to project files. Most people don’t have the same issues with Dropbox that you do, so the engineering decision L&L made is the right one for them.
This wasn’t a choice between Dropbox and some other service. This was a choice between Dropbox and nothing (other than iTunes), because despite what you think about their service, at the end of the day it’s the only one that gets the bits synched without breaking them. It doesn’t matter how ideologically superior other services are if they break your data on a regular basis.
What you’re really asking for (demanding, really) is that L&L completely re-architect Scrivener’s file format, which would violate some of the basic design goals and features that are possible in today’s Scrivener without offering any sort of recompense for the users who don’t care about mobile synchronization. Your demands would affect ALL of Scrivener’s users, and mostly in a bad way.
You can make that decision for yourself. You can’t make that for the rest of us.
It’s not that anyone wants you to go away – it’s that we want you to acknowledge that your particular concerns don’t somehow make you morally superior to the rest of the L&L user base and certainly don’t give you the right to keep badgering L&L and the rest of us on this subject. You’ve asked. L&L has responded. If you’re not happy with that, join the rest of us who have some aspect of Scrivener we’d like to see changed but L&L has heard our views and decided otherwise. And then we continue using it without complaining. Using Dropbox doesn’t make us stupid – it simply means that we don’t have the same set of priorities and concerns you do.