Ye the cleared path thing is strange.

However, I'd say that either both Eris and Pluto are planets or neither, so it is not too strange to reclassify "planet" to exclude them.

You could go with "9 biggest objects by volume in the sun's orbit" or something equally arbitrary.

The Scientific American version has prettier graphs but this paper [1] goes through various measures for planetary classification. Pluto doesn't fit in with the eight planets.

[1] https://www.researchgate.net/publication/6613298_What_is_a_P...