Per definition a dwarf planet is:
a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape1, (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite.
The Wikipedia page for 2007 OR10 states three possibilities for its dimensions:
- 1535+75−225 km
- 1280+210−210 km
- 1200+300−200 km
Which is all minimum 1000km in diameter. So how can you still doubt the hydrostatic equilibrium for such a large body?