Both of you are likely correct. DI carbon deposits is still an issue but almost assuredly overblown by internet forums. I took a few weeks to go over many posts on the Hyundai boards and have come to the conclusion that nothing is a cure... not low Noack, short oci, catch cans, synthetic oils, Top Tier gas, nothing. Most members of these forums are "car people" who care to go an extra mile for maintaining their vehicles. In line with this is going with what has been considered by industry publications, studies, and knowledge sharing that a low Noack Synthetic and Premium fuel is the way to go.
If only this were the case. Many of these forum members are now very disappointed that they've been using a "Full Synthetic at 5K mile oci, Premium fuel along with some using a catch can" and now have carbon deposit issues or are showing drivabilty symptoms associated with it. When these guys post this news, the Conventional oil users pounce, citing that they have no issues and have running the cheapest dino since new and are now near 100k miles... Then when a member whose run Conventional all along gets deposits, the Synthetic crowd pounces with their views, chastising the guy for going Conventional and not using low Noack Synthetic etc. All of this language is very predictable. Unfortunately GDI deposits are not.
In all, both, Synthetic and Conventional oil users get... and dont get deposits. I now doubt oil plays a significant role. So far, after owning a few Hyundai, I've been lucky. And to be honest, my T-GDI Santa Fe has over 100k miles and is the most reliable vehicle I've ever owned.