Yes, Washington St. and Oregon St. are playing at a "power conference" level, but you can't/shouldn't qualify as a conference with only 2 members.

Also, if you add their 4 "expansion" teams (Boise St., Colorado St., Fresno St., San Diego St.), their Central Mean rating drops to 70.64 which puts them firmly in 5th (with quite a bit of a gap behind #4 ACC and a bigger gap ahead of #6 AAC).