Here’s the relevant part of their website for reference:
If you request an extreme number of keys and you are not offering Steam customers a comparable deal, or if your sole business is selling Steam Keys and not offering value to Steam customers, your request may be denied and you may lose the privilege to request keys.
I find it hard to believe Sony would run afoul of these guidelines. I’m not sure what they mean by “if your sole business is selling steam keys”. Maybe referring to shovelware ‘developers’ that use steam for laundering money, if I had to guess.