The stretching I'm referring to is the slider seen here in the IK Constraints settings for individual bones, not the "Stretch To" constraint:
A while back (a little under a year ago now I think), I heard that the this stretch function got updated so that it will only stretch on the Y-Axis. Back in the day it didn't do that. So the Y-Axis stretching managed to stick around up until 2.79 RC2 rolled around. It seems that the feature has been reverted back to how it functioned back in the day, where stretching would enlarge the bones on all axis instead of the Y-Axis as shown in this video:
I suppose this could debatably be a bug, but it seems like this is an intentional reversion of a feature. All I want to figure out now is if (and how) I can get the 2.78 functionality of the stretchiness back into 2.79rc2 if it's at all possible, because my rig benefited greatly with this much simpler way to apply stretchy limbs to a rig.