IANAL but I don't see anywhere in the PATENTS file where it restricts this issue to software patents. In fact it explicitly talks about any software, technology, product or service.
That means you essentially can't sue them over any patent ever. Not just software.
With Facebooks history of "liberal borrowing" when it comes to product, it would be prudent to assume this same strategy might be applied to non-software products and services.
I completely understand why WordPress is doing this. It makes a ton of sense. WordPress powers some ridiculous percentage of the web. They are doing The Right Thing (tm) by not stopping every single one of those users from bringing a patent complaint against Facebook. Software or otherwise.