You know, I was curious about that, because I heard both, so I googled it for a short while to see what I could dig up.
From what I gathered (see Youtube Vids here (thanks to Jeeqbit for his signature) for Yoshi-P saying there is no technical debt in the game itself from 1.0 and here, a discussion about a server issue that happened ~2 years ago), the technical debt may be localized in the backend structure of the game and not in the game client itself (can't say if that is the absolute truth, we are all lacking insight about the inner workings). That being said, I feel like this could be it, just look at how your friendlist loads, or knockback effects on a large number of affected entities.
So its either that there is different kind of technical debt depending on what kind of FFXIV you look at, or Yoshi-P lies.