That's also a possible explanation. I have always considered that since the Uchiha inherited the "Yin" power from Indra, then their MS techniques relied mainly on Yin dominated chakra (Sasuke's Susano'o was stated to be similar to when he used his genjutsu). When that excess Yin chakra is focused in the MS, it creates an imbalance with the Yang chakra from his eye and causes damage in the form of blindness. You could equate it to Creation Rebirth, a jutsu that effects the body, shortening your life. When the eyes are transplanted for the EMS, the Yang/Physical/Body chakra from the DNA of the eye itself will continue to be reproduced as seen when DNA taken from Hashirama's corpse was able to be put into Yamato, and the latter had access to Mokuton. When combined with Sasuke's own Yin/Yang chakra, the excess Physical energy ends up balancing out, getting rid of the blindness problem, yet also accounting for the merging of powers/patterns of the eyes.
However, this is mainly conjecture on my part. Indra was never shown/stated to have any issues with blindness, and Sasuke receiving 50% of Hagoromo's Yin chakra would pretty much invalidate anything I said, though I think he got some of Hashirama's cells from Kabuto.
I'm not ruling it out as a possbility, it's just that Hashirama's DNA has shown special properties that I doubt the Byakugou could replicate, such as increasing the length of Izanagi, decreasing the cooldown for KA, and increasing the binding strength of ET. And it's debatable whether or not Obito had some of Ashura's chakra which could have played a role.