If you are overcautious with privacy matters and choose Purism only to maximize yout privacy, then yes. I'm not that worried about privacy, and yes I use Facebook. (No whatsapp but mostly because it is not available for Sailfish/Maemo). The reason I would choose Purism might be having a Linux phone. To support open source. To have a phone which is capable to do everything I need. In my list, privacy is not in top 5.

Like I said about being different, I also think that the privacy thing also isn't big enough for a marketing argument. It is better than just being different, but not much.

Also, the having a smartphone mostly means being connected to online services. Many of them require account registration. So just having a smartphone isn't the thing you should do when overconcerned about privacy. Just stick to that old Nokia 3110, and keep it shut down and to be sure, wrap a piece of tin foil around it!