Wow, a whole new level of infuriating, but I figured it out.
First off don't use Wifi printing, you must be USB or TCP/IP connected. Do not select Bonjure if it's listed in your printer driver install process. Wireless modes are going to use AirPrint which will basically mean that you're printing to a generic Apple pseudo-printer.
Now, assuming you've already installed your printer and it's driver, just go ahead and delete the printer via settings, printers & scanners, etc. Then add a printer with the little +...then make sure you select either the USB or TCP/IP option:
View attachment 1404
Now, see that "Use: AirPrint" down at the bottom? That's the default, but that'll just defeat the purpose of this whole exercise. open the drop down and select "Epson SC-P800 Series".
View attachment 1406
complete the install and you should be G2G