Okay so I just checked the "missing" entries pasted by Chrono and all of them are either typos/caps changes (that I don't believe need translating at all, but is still there for comprehensiveness), or stuff that has changed between 673 and 674. These latter strings (most of them anyway) were marked as such (added/changed/whatever in 674) in the changelog, though it was admittedly confusing and has been reported to Sunshine. Then we started making separate sections to list changes for separate builds, and bumped the modified entries, as well as some new (a few) ones, into the 674 section.
About the changelog filename, I agree we could/should make different changelogs for different builds, but then again we would get complains because there would be too many files to manage.
To answer the O.P., I have to ask : are you checking everyday for a new changelog/new build? What's the issue if you didn't get an email (yet, the mail was sent this morning) about a new changelog? Do you take note of what you've worked on? We may not be helping, and I know everyone has their own way to get the work done, but it seems to me you're kinda confusing yourself here.
The changes in the aboutbox were bumped to 681 in case some of the translators missed them in 677. If you already translated it, what's the big issue?
Lastly, and I'll be speaking as a translator here, I also find it quite annoying to have to work on something that's not final and constantly updated. I don't find it that confusing though, but that may be because I *know* what has changed and what hasn't... To a certain extent. To another extent, I'm really just like you when facing the constant changelog updates and whatnot. And I'll give you this can be rather irritating