The white list always includes WiFi cards, but it may include other devices depending upon the other options available (like a TV tuner card) and how aggressive the manufacturer wishes to be. They make a significant profit selling $10 WiFi cards for 10x the price, so that has been their biggest incentive to do this; force the customer to buy optional hardware from the manufacturer. But even with that idea, they bungled it as a newer card purchased directly from HP would require a BIOS update that they do not have. There have been postings about that very thing--a customer buys a new card from them, paying the significant markup, only to find the card doesn't work and a "puzzled" customer service rep.
So, if HP doesn't take its customers seriously and wise up to this unfair predatory practice they've got going, then people need to be aware of it. If HP would issue a formal announcement of rescinding this white list and at least provide people on request an updated BIOS that removes this white list, then a posting like this one wouldn't be necessary.