Got bored, did some digging in their binary, they built using some of our our svn libraries (I know it’s our libs since the paths embedded for some of the source files are local to my computer 
) which makes it easy to track down
they ship openimageio 1.7.15 which means the code is likely from somewhere in between 2017-06-04 and 2018-08-27 which is indeed around the 2.79 time frame.
It would have been nice if they kept the code opensource, so it could get all the improvements blender makes easily, but they seemingly chose not to go that way. which is somewhat strange since they clearly lifted the GPL licensed bf_blenlib [1] so the closed source nature of eyesight is odd to say the least.
[1] the executable contains strings like Error! Could not get the Windows Directory - Defaulting to Blender installation Dir! , Error! Could not get the Windows Directory - Defaulting to first valid drive! Path might be invalid! and BLI_dynstr_append text too long or format error. that can only could have come from bf_blenlib