Sorry, that's ridiculous. Basically every major free software dependency of every major platform or application is maintained by people on the payroll of one or another tech giant (edit: or an entity like LF or Linaro funded by the giants, or in a smaller handful of cases a foundation like the FSF with reasonably deep industry funding). Some are better than others, sure. Most should probably be doing more. FFMpeg in particular is a project that hasn't had a lot of love from platform vendors (most of whom really don't care about software codecs or legacy formats anymore), and that's surely a sore point.
But to pretend that SteamOS is the only project working with upstreams is just laughable.