I don't think they're pretending. Open source software is a valuable resource for basically all major tech companies, and a lot of it is driven by major tech companies. Some kind of combination of open source and proprietary software will always be a thing for them. This isn't some major contradiction, they use either model based on the specific needs of the project.
This is why some think "Open Source" is too permissive since they see it as free/cheap labor to be exploited by huge corporations.
I'm not sure that I see it that way, but I can see their point.
Wow, I'll be switching from Firefox to Task Manager!