No insight into the change, but perhaps some insight into the "effect".
Heavier strings emphasize fundamental tones but provide less overtones. The HD Lights, developed by Elixir specifically for Taylor were designed to make Taylor guitars sound less "bright". Hold that thought for a moment.
Why not just go with medium strings? Taylor's sound-claim to fame is their overtones and resultant harmonics. If you put a .056 string on the bottom it kills off many of the overtones and harmonics that create sympathy with other overtone and result in "resultant harmonics" which make their guitars sound fuller, richer... and sometimes brighter. Putting a heavier bottom string on a Taylor can actually reduce the overall bass projection somewhat as it reduces overtone.
So, creating a hybrid set with heavier strings on the high end should have balanced out the sound but I think they found that overall it didn't and created more issues than it solved, possibly because there are so many variables across their line of guitars that it didn't make sense to put HD Lights on at the factory.
Just my opinion and speculation.
__________________
Assuming is not knowing. Knowing is NOT the same as understanding. There is a difference between compassion and wisdom, however compassion cannot supplant wisdom, and wisdom can not occur without understanding. facts don't care about your feelings and FEELINGS ALONE MAKE FOR TERRIBLE, often irreversible DECISIONS 
|