Well I also have to thank you for finding this abnormal behaviour.
I tried what you where pointing out.
Started a new program with one soft start WS467 and it send Extended Commands. Added a second WS467 on the same address and deleted it.
AHP reverted to the older On and Off protocol until I exited AHP and it again reverted to Extended Commands.
So adding a second WS467 did correct your problem until it was restarted and reverted back to Extended Commands. The old WS467 didn't recognize.
It looks like the "cleanup" when the second module is deleted is broken. However, closing and re-opening AHP fixes the problem. Yes, it is a bug, but I don't know if it is worth adding it to the list. Does it only happen with the WS467? Does it only happen when there is only one module in the AHX file?
There are already a number of "SoftStart vs. non-SoftStart" bugs, and I don't know if this one is truly different (we already know that you will have "inconsistent behavior" if you mix module types on the same HC/UC.
I haven't seen any signs that indicate X10 is still doing any work on AHP. I don't know if they have any developers left. If they are working on a replacement for the CM15A, my guess would be that they would be building new software for it. I could be wrong, however. Perhaps they will modify AHP to work with the new controller (or design the new controller to mimic a CM15A when it talks to AHP).