It very well could. Defining a planet as major or dwarf goes by its ability or inability to "clear the neighborhood", to control or remove objects of smaller mass in its orbital area.

225 AU is a long way, and the volume of space to clear goes up quadratically with distance; this object would have 50,000 times more space to clear than does Earth. The orbital period also goes up with distance [edit, reply is right that it's the 3/2th power], so so does the time between interactions with any particular object.

Multiply those together and you would have an object more than cubically (3.5th power) less effective than Earth at clearing its neighborhood over time, such that it may not have happened in the lifetime of the solar system.