Again, you are right about hash rate not being able to hide but it can be turned off and on and clearly visible wile doing so as unknown. The unknown on litcoinpool just shows the on part of unknown hashes not the "hiding" off hashes.
Show me where the 'Unknown' amount is increasing beyond a few dozen GH.
I routinely check that figure and it is the Chinese pools mostly adding the extra hashrate to the total LTC network amount.
Just me roughly look at it for a few mins today I can find spikes of 700GH roughly its all in the charts. Not just the online unknown in the pie chart you need to consider whats not online or "hiding" if you will.