That's already complete nonsense. The developers are just full of crap. Let's say there is a second-preimage attack for BLAKE-512. So am able to compute an input value X, so that BLAKE-512(X) = Y, where Y matches the difficulty and finds a block. If Keccac runs before Blake, I still need to find a l need to find an input Z, so that Keccak(Z) = X.
Furthermore, they claim:
LMFAO. These kids have no clue what they are talking about. In fact, the opposite is true. If one hash function is broken, it's possible to freely choose the corresponding 64 bit in the output. Oh guys, just quit this coin. It's pathetic and an insult to anyone capable of adding 1 and 1.
Did you miss the 'interleaved' word somehow? You need all 4 hashes to have last 4 bits zero to match the target 0x0000FFFF.. I'd suggest just reading the code.
However, using only last 64 bits of each of 4 hashes (and effectively only last 8-10 bits for PoW at current difficulty) kills the math behind their cryptographic security proofs.