I don't really think it abuses the term, since it doesn't require a backlight to display things, it is technically correct to call it e-paper. I also remember the people at Pebble discussing the differences between e-Ink and e-paper when it first came out. It's not like they hid how the Pebble's display worked.
Besides, an e-Ink screen would be a horrible experience given how the display gets used in the Pebble watch.
It always seemed purposely misleading to me. Heck they don't even use the term LCD in the technical specifications... which is odd because that's what it actually is. And it did work as I had multiple friends, including several technically minded ones, who were misled by Pebble's terminology and thought it was an ereader-quality display.
Besides, an e-Ink screen would be a horrible experience given how the display gets used in the Pebble watch.