I'm curious as to why they made this document public. If I owned almost 6% of Yahoo!, I wouldn't do anything that would publicly make Yahoo! look even worse. I would discretely contact the company and have it dealt with quietly. Additionally, why bother lying? I doubt Mr. Thompson got the job due to his 20 year old CS degree at a tiny liberal arts college.
But lying about the degree, and that's easily verifiable, just doesn't look good for him.