Not sure. I feel this might be a pretty odd experience for users?

As much as I agree with truncated titles being suboptimal, omitting it completely doesn't sound like a more user-friendly solution. Imagine you're confronted with an “Apply ch…” dialog that doesn't provide you enough context to know where you are at first glimpse. Even the truncated title might help users figuring out where in the process they currently are.
Also there's normally a title field in place, which means, when you're hovering the truncated title with your mouse you'll get a tooltip with the full title.

@Whatamidoing-WMF How many times have you been coming across truncated titles and where?
Inclined to make user life's better on a case-by-case base than by proposed approach in general.

The user in this discussion says, the dialog shouldn't be larger, I'm actually not convinced, that this isn't the right thing to solve the issue.
@Jdforrester-WMF Where does the 500px value originate from, maybe you can shed a light?

@Volker, I get truncated titles in German:

and Russian:

and, I imagine that you'll see it in just about any language, if you pick just the right (wrong) combination of screen size, font size, and zoom.

@Whatamidoing-WMF Thanks for the screenshots!
The combination is possible, but in my understanding and experience it's a rather rare one. Normal browser zoom not text only, but everything accordingly if you're not explicitly setting the zoom to text only (Firefox is one of the browsers where that's still possible).
What you're bringing up is still interesting for us to hunt down, as we might need to find a way, to make the dialogs mobile-friendly.
From my POV it's not a useful idea, to omit the title in general for all dialogs. It's an exception of German language that title and primary action are labelled the same. In Russian from your screenshot, there's already a discrepancy. So we need to decide from case to case about the best solution…