I don't think the techniques have changed. At least, not that drastically.
I think BigPoppa explained what you're seeing, here:
It can be as simple as this: when you see a lot of kids not turning their heads, that probably means they're playing catch-up.
Waaaay simplified, what is normally coached goes something like this: (a) stay on his hip (b) if he gets away from you, get back to him (c) if you're in good position and he turns, you turn too, find the ball, and intercept (d) if you can't intercept, knock it out of his hands before it counts as a catch (e) if he makes the catch, strip the ball and get the fumble (f) if you can't strip it, tackle him. [some coaches do not emphasize (e), but go directly from (d) to (f)]
In other words, you're seeing our coverage break down at step (b) too often. We need more speed. Not different coaching.
Go Vols!