Yes, HG uses different end cap than XDR, unfortunately.
I ordered this wheel set and already received it. My plan is to purchase 3-pawl steel HG driver, as I already have the end cap laying around if I can find it.
Ironically, Planet Cyclery had the required end cap for real cheap.
I might be wrong, but I think this is the end cap (part number Hwa00100s2192c) one would need when converting to HG.
This is a replacement Dt Swiss 240 Rear Right Axle End Cap 142Mm. Conversion From 135Mm (Hwa00100s2192c) This item is used on the following models:... S115900020
www.performancebike.com
And a steel HG driver I ordered, part number - HWRAAMWSS0342S
Alternatively, one could purchase HG driver with the end cap, but for the life of me I can't figure out whether it's steel or aluminum version of the hub.
internal cable routing with Polycarbonate cable connector\n precision machined alloy mast with Integrated seat collar\n Microadjustable head with steel bolts\n adjustable air sprung hydraulic open bath cartridge\n cable and housing included\n remote not included\n length is measured from saddle...
carsoncitybikeshop.com
Also, there are two versions of the HG driver (11 speed road and MTB). Each of them is using a different end cap as far as I know as the length (width?) of the hub is different.