To my reading, there are two separate items: a copyright license and a patent grant. - The former allows you to make copies of the software - The latter protects you from Facebook claiming patent infringement arising from the use of React Native (aka, Necessary Claims). It doesn't necessarily mean they have such patents but if they do, you are protected.

So if the reciprocity clause in Facebook's patent grant is a problem, all recent MIT licensed software out there without a patent grant would also be off limits.