That sounds exactly like the old Morrowind loading system. It was relatively seamless at the time for traveling about outdoors, sans the mini loading between these cells. It used to take a few seconds back in the day it was released but with modern SSDs it takes a fraction of a second.
Oblivion and Skyrim made this for the most part invisible. But loading times for indoor transitions still existed.
That’s sad because TT’s games were quite good, I think they hit their apex at Lego Marvel Superheroes 1. Awesome open world, a ton of characters, and lots of exploration in addition to the normal level quests.