Well, turns out it opens just fine over here
.
It might take a good long while on slower devices, but it will open & work when it does. Subsequent openings will use the cache, and should be much faster, as long as you don't thrash the cache by requesting a formatting change that requires a re-render.
FWIW, it takes a whopping 4s and change to open on my desktop, which is far faster than @poire-z's gnarliest test books, I think ;p.
Code:
07/22/19-19:16:12 DEBUG CreDocument: loading document...
07/22/19-19:16:16 DEBUG CreDocument: loading done.
(And generates a fun 14MB cache file
).