Weirder and weirder. Sounds like they really don’t want to do it with conventional dimensions. Or whoever is designing the head is inexperienced in the conventions, just trying to make it look OK on the CAD screen without considering the implications.
Not very mod-friendly, nor desirable as a host.
Suggestion: lay it out for 17mm, just add more ground ring around the edge to fit this thing, however it eventually turns out. Be it 19.2mm, or 20, or whatever, routed out to suit.
I like the hole in the middle, allows head spring bypass straight to LED + wire, in case they use an unsatisfactory spring. I would prefer that they retain the stud instead, it is electrically and mechanically superior to any spring.
Then please sell me some routed out to 17mm.