Why would you expect Samsung to give any lip service to a strong competitor in a huge publicity opportunity? Especially when their primary message was about open standards, as you say; and Homekit is not really an open standard in the way ST and Samsung talked about. You can’t take a Homekit compliant device to another ecosystem and tap into it like you can Zwave or Zigbee.
I’m fully iOS/iDevices in my home, and I expect them to integrate with Homekit (especially based on the linked post below); but I wouldn’t expect them to incorporate that into a big Samsung moment given their history. I understand the skepticism, and I share it; but this was not the time or place to make any such commitment. It’s also very early for Homekit as there’s nothing out there yet.