I suspect/ near darn well sure actually that they copied Epson's pattern because with that pattern and a simple optical detector, they can easily determine which nozzle in the array is not working. Each stairstep represents a unique nozzle, so by scanning the output with a simple optical detector in coordination with a timing strip, they will know which nozzle is not working and how it should be compensated for.
About Panos. For a long while and still do, whenever my Epson uses WiFi it is horribly slow. The Canons on the Wifi is perfect.
I thought it might have been an older router but no. I wonder if the limitation of the Panos has to do with the operating system guidelines that Canon adheres to or Epson does not. Via Ethernet or USB, everything is perfect with the Epson.
BTW, I've tried two routers with the same results. A Linksys WRT54GL running Tomato as well as stock firmware as well as a Linksys WRT1900AC. Same issue, OK on text but frightfully slow on images with the Epson.