Going into the heart of darkness to understand the darkside is exactly what Ulic did. It seems to be something Veitch was interested in, if he used it more than once.
I’m going to infiltrate the Sith from within and slowly walk the path, I won’t fully go over. He gets a taste of power like a drug and it’s so seductive he loses himself. Then he slays his brother, a kinslaying there is no going back from that. Nomi took pity on him and cut him off from the force.
Yoda warned Luke. not to walk the quick and easy path. Forever will it dominate your destiny, consume you it will as it did Obi-Wan’s apprentice.
Dark Empire was first. The Ulic story is an in-universe point of comparison/warning for the Luke story in Dark Empire, then it was fleshed out in Tales of the Jedi.
The infiltration thing does make it a little different, but because of Palpatine, the scenario and outcome of it are still similar to Return of the Jedi.