Earlier quoted context omitted.
I don’t think he killed it “because it wasn’t NeXT software”. I think he killed it because the market didn’t support it (MS Office showed that an ‘everything but the kitchen sink” solution could conquer the market, leaving only breadcrumbs for smaller parties) and to focus the company.
But MS Office is sort of the implementation of what the article describes, with it being thoroughly COM based. You can embed pieces of Office in your software, or pieces of your software in Office (including saving its state in the MS Office's documents).
Also (and possibly alongside “we sell Word/Excel separately, too, and want it to be everything but the kitchen sink, to prevent others from providing missing parts”) the answer to that may be “because the UI of OLE-embedded parts isn’t as smooth as it could be”. Outside-in activation (which, reading http://preserve.mactech.com/articles/mactech/Vol.10/10.08/Op... doesn’t seem to be required with OLE, but I haven’t seen otherwise) means you have to click multiple times to start editing (clock to activate an OLE control, then click to start editing it)
OpenDoc promised much more, but of course, the market didn’t want to deliver it at the time, and we also don’t know whether its promises really can be fulfilled (Cyberdog was cute, though)