While this maybe true, none of what you mention has changed recently but this ranking did. This ranking change at least points to a trend. Maybe the percentage

While this maybe true, none of what you mention has changed recently but this ranking did. This ranking change at least points to a trend. Maybe the percentage of mobile use is increasing at faster rate on FB vs Reddit, recently. But according to the nextweb link someone shared in this thread, FB had nearly 90% of their traffic via mobile already in 2016.