I'm 99% sure that google supports openbsd because that also includes libressl, openbgp, and other solutions in addition to openbsd - it's a "generally good for the internet" scenario.
Maybe so, but the bigger question is whether or not the financial contributions that these behemoth companies make matches the value that they receive.
At least they give something back. As another example, Sony took FreeBSD, added some proprietary bits on top (like their own graphical API), turning it into the PlayStation operating system family. They've made billions of dollars on that (saving countless millions by not having to develop an OS from scratch), and gave bupkis in return. Try finding them in any of donors lists. Last time I mentioned that I was downvoted to hell because apparently it's wrong to ask giant corporations to support the foundation they're building on top of, and I'm a communist for doing that.
Perhaps it should reflect the value they receive, they're there to make a profit. It might be better to ask whether they would receive even greater value if they put in more, and I believe they would, but perhaps they've done the maths and think differently.