You've got a point but unless you're a visa officer yourself you won't know for sure how they think or what and what not they would consider before approving a SP. Imagine it this way if a huge establishment is willing to produce you this legal binding letter, doesn't it mean you're immensely desired or doesn't it speak for itself you can easily always find a job in your field back in your home country provided you are a top candidate, especially if you were previously refused cos of this reason? As a matter of fact, I've seen and read about many applicants that got their approvals cos they produced this document and other supporting documents. The truth is no one really knows how the visa officer will think or view your application cos its not something generic. Hence, I disapproved of your statement that those applicants wouldn't have got approval cos they had future job offers, as this isn't evidentially a true statement. It might be just your personal take/theory...