Open a typing test elsewhere and hit refresh a few times. Notice how fast you start recognizing patterns - the same word clusters, the same punctuation quirks, the same generator fingerprint. That's what happens when "random" text comes from a small algorithmic pool: it stops testing your typing and starts testing your memory of the generator.
TypeClash doesn't generate passages on the fly. It pulls from curated pools, and - this is the part that matters - the pool you draw from depends on what you're doing. Ranked solo matches pull from one pool. Multiplayer races pull from another. Season levels pull from a pool scoped to that specific level, so difficulty progression is authored, not accidental. There's even a separate pool for practice ("infinite") mode, so grinding for comfort and grinding for rank never dip into the same well.
The reason this matters more than it sounds: a shared, farmable pool is a leak in a competitive ranking system. If enough players could predict or memorize what's coming, "rank" would start measuring memorization instead of typing. Scoping pools by mode closes that leak without needing every passage to be freshly generated - which, ironically, tends to produce worse text (generators are bad at natural rhythm, real writing isn't).
Randomness isn't actually the goal. Unpredictability with quality control is.