It's more like, given a good job market and low barriers to entry, the percentage of candidates who are not qualified will greatly outnumber the good candidates. Good programmers might be looking for work for any number of legitimate reasons, even in a hot market. Doubly so if you are offering a premium on compensation or otherwise trying to make yourself more attractive to applicants (which four hours of take home is the opposite of). The signal to noise ratio is just lower the less attractive you make applying to your company.