Interesting. I was wondering why there is an adapter specific to the ED72 so I searched and found this thread on SGL that confirms the thread is different from Skywatcher's other scopes. No idea why they changed it.
https://stargazerslounge.com/topic/3...-just-arrived/
I also noted that the ED72 owner complained of a lack of focus travel. Apparently there is only about 40mm in this scope, which probably explains why you couldn't reach focus with your 2" your erecting prism as noted in another thread.