I'd be surprised if the walking dead state of Open separate from Libre wasn't caused by in-house tools somewhere that just never got ported to Libre, or that are somehow inherently incompatible with that fork. Symphony is certainly a prime suspect for the original "version some in-house stuff got built on".
The question "do we really want to port yet another minor improvement/fix from Libre to Open instead of porting our own grown mess from Open to Libre?" can be answered with a short-sighted "yes, of course!" any number of times. And Open cannot be formerly declared dead as long as this form of contribution keeps happening.
IBM discontinued Lotus Symphony nearly 10 years ago. OpenOffice continues because the Apache project chairs in place hate the GPL, and even worse, they hate admitting they lost. It's a moral/pride thing rather than a practical or business thing at this point. But IBM was the reason it exists in the first place.
> OpenOffice continues because the Apache project chairs in place hate the GPL
LibreOffice isn't even GPL. It's Mozilla Public License (MPL). Still copyleft, but much more weakly so, because only MPL source files are required to stay MPL. You can mix MPL files with even proprietary source files, and you only have to distribute the changes to the original MPL files.
Though I suppose that might conflict with the Apache foundation in general. Don't they require Apache license for all their software?
Judging from the simplified fork graph in the article (likely greatly simplified, I admit), I'd expect something depending on Symphony to be far more compatible with current Open than with current Libre. But sure, the licencing difference might very well be a part of that.
The question "do we really want to port yet another minor improvement/fix from Libre to Open instead of porting our own grown mess from Open to Libre?" can be answered with a short-sighted "yes, of course!" any number of times. And Open cannot be formerly declared dead as long as this form of contribution keeps happening.