I don't know of any detailed analysis, but apparently the block is based around the patterns of memory access etherium mining produces (etherium's proof of work is designed to be memory-bandwidth limited to discourage the use of FPGAs and ASICs in mining, on the perhaps mistaken basis this would prevent the kind of centralisation present in bitcoin mining). It's quite plausible that the implementation of the proof of work could be adjusted to avoid this detection, though depending on the level of sophistication of the recognition it may have been difficult to do without impacting performance.