Well, yes, the "meta" part is just how the actual key is broken down. What may be different is that decryption involves more than just figuring out the values for the key, but also its breakdown.

For example, if the bit length breakdown of each key chunk was 17, 15, 23, 12, 20, 19, 22 you would have a 128 bit key. But its not as "simple" as determining the 128 bits. There are 7 key chunks, and the length of each key chunk and the order of their bit length is essential to decryption.

The same key might be guessed with 6 chunks of different bit lengths. This won't decrypt it and in fact it won't even come close or give any indication that it was the correct key sequence.

So, this is what I mean by a "meta" key. There is an additional "dimension" to the key, this dimension means that there are an additional few magnitudes in the keyspace than simply the bit length.

So, in a simpler scenario, a 32 bit key, which normally would be pretty easy to crack, is much harder if you also have to determine if it breaks down: 5-13-9-5 or 17-15 or 9-32 or 5-7-3-6-11 or... The number of permutations are staggering.

Is there another cryptosystem that uses something similar?