Found
this post on Cloudy Nights with some comments by "Mr Filters" David Knisley. Reads like he hadn't used the HP version of the OIII at that stage, and had preferred the Lumicon OIII over the non-HP OIII from DGM(?). He mentions that from the specs on the HPOIII it looks like it'll be similar to the Lumicon and Thousand Oaks.