Tannehill has been on the receiving end of a handful of very late hits this season and none have been flagged. One against Baltimore last week had Tannehill release the ball and complete his follow through, after which the defender took another step, then launched and hit Tannehill with the shoulderpad right in the lower facemask (itself a penalty, regardless of timing, due to the "head or neck area" rule).
I've seen late hits on Brady and Manning as well, this season, so my very subjective opinion is that roughing penalties are down and, more to the point, toned down this year.
Trying to find some numbers to back up my gut feeling proved difficult. Overall "unnecessary roughness" penalties are way down this year, from 13.5 per week to 10.2 per week (
source).