This has been a rumor for a while, it stemmed from SkyWest trying/getting approval to do an abbreviated course for people with a type rating. Obviously SkyWest saves money on the type and transfers it to the new hire. The bonus is designed to make the first year pay more bearable by effectively increasing a line holders pay by $5 a hour (90 hours a month for a year / 5000).
Theres not many CFIs to be had, there are more people that have gone through airline training and wanting to make a leap from their current carrier for whatever reason.