The blog isn't quite right. HTTP/2 requires ECDHE (or DHE, but don't do that) with an AEAD, which means one of the GCMs or CHACHA20_POLY1305 if you have it. It's written as a blacklist, but this was the intent.
What's going on is Chrome and Firefox don't do AES_256_GCM (but Chrome will be adding support in the next release, see [1]), which means it was picking a CBC mode cipher and HTTP/2 wouldn't allow it.
SSL Labs is, in my opinion, wrong about incentivizing AES_256_CBC over AES_128_GCM. The CBC mode ciphers in TLS are composed wrong and very very difficult to implement safely. They'll be gone in TLS 1.3.
What's going on is Chrome and Firefox don't do AES_256_GCM (but Chrome will be adding support in the next release, see [1]), which means it was picking a CBC mode cipher and HTTP/2 wouldn't allow it.
SSL Labs is, in my opinion, wrong about incentivizing AES_256_CBC over AES_128_GCM. The CBC mode ciphers in TLS are composed wrong and very very difficult to implement safely. They'll be gone in TLS 1.3.
[1] https://groups.google.com/a/chromium.org/d/msg/security-dev/...