There is definitely a PR aspect in this approach. However, there are legitimate reasons to promote a diverse recruitment policy. For example, such a policy may encourage applicants who share these values, or feel that Seattle is more likely to give them an opportunity, to prefer Seattle over some other employer. After all, the team has to compete for talent with many other businesses and if they legitimately become number one choice for groups of candidates, their chances of getting the best improve, at least among that group of candidates.
Of course that approach is not without risks. It may alienate some who feel that they are not given equal opportunity or who believe that they would be seen as quata hires and thus undervalued. Any strong value statement also includes the risk that if the organization fails to uphold those values, it may cause backlash.
One can look at Nike’s campaign with Colin Kaepernick, Gillette’s #meToo ad or recent SAS advert as examples of difficulties a business can face, and advantages that may be reaped, if the company decides to take a stand in respect of polarizing issues.