You're nitpicking the term RNG.

There is a randomness factor between fights and between groups on exactly when, during which mechanic, Titan actually goes invuln and jumps.

I've had transitions where Titan literally doesn't jump and just teleports to the middle. I've had transitions where Titan almost does his last action mechanic twice while invulnerable, making the transition last an excessively long time. I've had transitions where he goes invuln for like >5 seconds while finishing whatever he was doing.