I asked the experts on this thread some time back (thanks HansenDeHardwarezone, chrislenoodle, KingKenny and Son-Y-noS), and I eventually got Jann Paul's Decagon Round 10 White Series. The process was really really fast for me, apparently I'm one of the lucky ones: the digital renders took one week, the plastic cast arrived in one week, and the custom cut diamond (which I was told would take two to three months) arrived in the following week...surprise surprise. They said that most likely, they had enough leftover rough diamond to cut my Decagon, hence it came so quickly. The ring setting wasn't even ready at this point - gonna be another four to six weeks from now, although they've already ordered it.
Sharing the images here (taken using my handphone, S10+ doesn't have the best camera) for reference, in case any of you are still undecided! The cut is really on another level. Of course, you won't be looking through the scope when your partner's wearing it, so let them show you the diamond's performance in normal daylight / office light. I suppose the scope images let you sleep a little better when you know that your money is well-spent (guess this is subjective).
ASET Scope:
Diamond Magnifier (top) - this is your "starburst" 10 arrows:
Diamond Magnifier (bot) - this is your 10 Hearts & Arrows: