oh, forgot to ask how large your fruits are. The Hachiya is a large fruit, about 3"-4" long, also says they ripen from Nov-Dec so yours seems to be ripe early.
I have a rootstock tree shoot on my Matsumoto wase that I let grow out until it fruited, and it has similar shaped fruits, but it is very small, about 1-2" long. Here's my rootstock/sucker fruits.