They do apply to all codecs, absolutely. Some just have historically more usage, so the encoders might behave better. There are still bugs though, I do remember

They do apply to all codecs, absolutely. Some just have historically more usage, so the encoders might behave better. There are still bugs though, I do remember hearing about some device producing an H264 stream that another device couldn't decode in HW. It's still not perfect. Also, as many people have pointed out, VP8 is a more complex codec than H264, so harder to test coverage of all features, especially as most applications (especially on desktop) are not really doing RTC, which is quite a specific use case. And phones DO have VP8 encoders. It's just that iPhones for historical reason don't have one. Pure speculation from my part, but I'm guessing they'll do AV1 someday as Apple is working on the spec. But in general, even though HW encoders would be awesome for all codecs if they were working well in all situations, the reality is they don't always work, you usually need to build lists of HW that is supposedly behaving well with your use case. All advanced features (eg spatial layering) are tricky to implement in HW and are usually not configurable, so SW codecs will still have quite a lot of usage for the sake of quality.