Long story short, it was the result of one of the 9001 flame wars between Greg and mDiyo. There was a very heated, and silly (for both sides) argument on OreDictionary conventions and specifications.
Eventually, it ended in a compromise where Greg agreed to not mess with mDiyo's mod stuff and vice versa. Although some say that GregTech is incompatible with Tinker's Construct, they load OK together, but there may be unexpected and unresolvable issues that may occur. Don't expect many to help you with these issues since the modded MC community is still somewhat polarized about that, and we usually don't want to reopen the can of worms and restart the flame war, so don't try to talk about that.