Well, few months back we had a session in Monopoly when some weird bug happened. Dice numbers disappeared. Dices were rolling but without those black dots. Game was still running and showing the results. I'm sure someone recorded that on video, and probably it has happened more than once. You can imagine people reacts in the chat.
And your question. Why would they need to have an RNG for dices? I'm asking the same. My guess is cause they have extra multipliers for super high wins making the rtp bit higher than in normal sic bo.