From the looks of this, it seems that the PCB/plate is being attached to the case with through PCB/plate screws into the gap between the F-row and the Num-row. I can't tell from the pictures, but it would seem then that the bottom of the plate/pcb must be secured with some tabs (or screws with a lip) that lip over the lower part of the plate to hold it in the case.
If that is correct, I've seen this method of holding the plate/pcb before in the MKC Geekey 87A. That's interesting because the MKC Geekey 87a shares its PCB and plate design with the Ganss GS87 and Noppoo Mid 87, which are also rumored to fit in a Filco case.
I have an MKC Geekey 87a (non-working) and a Ganss GS87 on order (to donate parts into the MKC case). I'm almost willing to order this case when it is available in the Doyu store just to try and confirm. At the very least, if it doesn't work I'll have an excuse to buy a Filco finally.