What triggers the jackpot or superblock? It doesn't sound like it's really random because you mentioned it's paid out when the "certain criteria" is met?
I guess it still based on the block hash. So if the block hash generated (or seeded) random number fall into certain range, the superblock will be generated. The difference is that before the previous block hash is used. This one still use the previous block hash, but the generated superblock will be paid to the finder of the previous block, so there's no chance for someone with bigger hashrate to profit it. Thus a "fair" or true randomness.
I read again the Q/As from OP, yes it is the great idea to have true randomness.