Are you sure? I just read this on their rewards website.
"*Companion Pass qualifying points are earned from revenue flights booked through Southwest®, points issued on Southwest Rapid Rewards® Credit Cards, and base points earned from Rapid Rewards Partners in a calendar year. Purchased points, points transferred between Members, points converted from hotel and car loyalty programs, and e-Rewards, e-Miles, Valued Opinions, and Diners Club, points earned from Rapid Rewards program enrollment, tier bonus points, flight bonus points, and Partner bonus points (excluding bonus points earned on the Rapid Rewards Credit Cards from Chase) do not qualify as Companion Pass qualifying points."