TeeS,
To narrow it down I was doing some recurrent at DON a few years back when the now H145 was being introduced.
My instructor was going through the pain of OEB/OSD with EASA.
His thoughts were in line with yours. EASA wanted to make the H145 a separate type!
I thought this was all part of the design philosophy - commonality. Especially with the Helionix.
Somewhere there is a "choke point" - pun intended.