Perhaps someone deliberately messing with their version string, e.g. testing the software to make sure it handles "unknown" or "future" release cases properly?
My immediate thought is that this is spoofed. I doubt anyone at Apple would be silly enough to allow software on an unannounced OS to freely send out analytic data. I expect they'd have some sort of filtering applied either right on their dev/test machines (something like Little Snitch, though surely built in-house) or at the network level.
> I doubt anyone at Apple would be silly enough to allow software on an unannounced OS to freely send out analytic data
...and you'd be wrong. It is very common for Apple to test its new browser versions on the public internet and for those version numbers to show up in the logs of popular Apple web sites. It's one of the ways that Think Secret could confirm that a new version was on the way.
Certainly not much if anything at all, but it's mildly interesting to note that it identifies as 10.14 and not, say, 11.0.
Anyways there is surely something strange brewing for the next macOS, as Apple has repeatedly noted that "macOS High Sierra will be the last macOS release to support 32-bit apps without compromise", without specifying what kind of "compromise" might come up (see https://developer.apple.com/news/?id=06282017a )
I think you might be reading that wrong - should be "Without compromise, macOS will discontinue support for 32-bit apps". The only compromise should be not upgrading to 10.14 and staying on 10.13.
Why would they not allow internal software send out analytics data? At this point it is common knowledge that Apple is working on a new version of OS X that will come out next year.