Each manufacturer has a different implementation of HDMI-CEC. Samsung's version is called Anynet+, and Sony calls it "BRAVIA Link" or "BRAVIA Sync" depending on some factors. Overall, the implementation is supposed to be the same. However, there are some variations. My understanding is what you picked up on was a design decision for Anynet+. I'm not privy to all the details that go into it, but that's my general understanding.
seriously, this is ridiculous.
I upgraded my main TV from a 40" Bravia to a 55" Samsung 7150.
I also have a Samsung Soundbar with wireless sub.
For whatever reason, the soundbar works great with the sony TV, but the samsung cannot communicate with it in the same way.
Airnet+ is configured, the TV "sees" it, and can use the vol +/- to turn the volume up and down (with some humongous garbagey animated banner on the screen, which I already hate). When I turn the TV off, the soundbar will turn off, as well.
Turning the TV ON, though, will not turn the soundbar on. This worked fine on the sony. Not on the samsung.
The "solutions" I've come across are this:
1) Use optical cord for audio, which will allow the SB to turn on when it detects a digital signal from the TV. Turning the TV off, though, the soundbar needs to "not get a signal for 20 minutes" at which point it will shut itself down. This is garbage, but OK. Oh wait, though... this needs me to configure the TV as having external speakers, which then means a separate remote to adjust sound.
2) use HDMI, and enable Anynet+. This allows the TV remote to adjust the soundbar volume, and will allow me to turn the bar off when the TV goes off, but turning the TV back on requires (surprise!) the 2nd remote to turn it back on.
At this point, the sound and TV are BOTH SAMSUNG.
When one half of that equation was Sony, it worked perfectly. I cannot believe that I've lost functionality by making both units the same manufacturer.