That's what I did what you suggested in your Edit.
I was looking for the option since Sync was supposedly updated to handle v0.19 and a handful of instances were already on that for weeks now. Never found the option. I just hoped a fix will come until my main instance is upgraded.
But anyway, the main thing I can use it with this workaround.
Have been running the betas and RCs on my instance and the new sort methods didn't show until 0.19.0 release, I'm not sure why. And then only if you have logged into the web version and set it. I personally never see myself using the "scaled" sort as it's all ~2-4 month old posts with no comments. So anything now would be like thread resurrection in the web forum days.
I dunno. I use it since I can and (at least for me) it's awesome. Finally fresh posts from little communities besides the big ones, far more diversity. I love it.
I wish I got posts that weren't so old, because in theory it would be perfect to get fresh posts from smaller communities. Instead I get threads that have died months ago and any interaction would be a resurrection unlikely to get any notice.