Someone said in one of the other threads that HD doesn't sell their engines to other manufacturers. Perhaps that's the deal: Morgan thought they did, and then they "had to" choose something else?
Or perhaps they found out that the S&S delivered more power/torque?
Perhaps it simply means you will be able to choose another of SS Cycle's engines. More power, less power, different setup aimed at touring or race track or something.
As you can see, I'm with you on the speculation part. The engine choice in "the first year" was something I took notice of as well.