The Genesis Mining disclosure was more descriptive:
“Zcash is still an experimental technology. We are working on a GPU miner, so in theory it’s possible that we are not able to deliver the promised hashrate. If we are not able to deliver the promised hashrate two weeks after expected Zcash mining start (28th of October 2016), you will be eligible for a full refund. But we are very confident that we will deliver in time so that you can start mining from day 1, with the best possible algorithm available, and perhaps even with a higher hashrate than currently advertised.”
The problem is that The Toomim Bros Ltd. did not define what delivery meant in a legally satisfying way, and instead mentioned that no refunds would be given.
Customers who purchased hashpower have defined delivery as: Mining Zcash consistently at purchased hashpower from the immediate release of v1.0.0.
The Toomim Ltd. has defined it as: delivering the total hash power purchased within the timeframe specified.
The problem is that Zcash difficulty and exchange price fluctuates quickly. Speculation had made Zcash worth much more from the start and as time increases the difficulty increases (complicated with the slow start). Many users were attempting to take advantage of early mining to make a profit from early speculation. After the slow start is over, returns for a given hashpower will slowly diminish making earlier mining more profitable. This means that a flurry of 1000 Sol/s at the end to “catch up” may not be comparable to a steady 500 Sol/s hash throughout the entire time period depending on if the difficulty more than doubles during that timeframe.