Don't make me laugh. I have 20 years in The City to your 10.
Calling an instrument a futures contract and not permitting short-selling goes against advertising standards.
I expect to be able to short a futures contract because I know the price is going to go down.
"The City" ?

sorry to break it to you, but 20 years as a shoe shiner in "The City" doesnt mean much. Anyone who worked on the street will realize how your rant makes as much sense as a uwe boll movie.
if one is forced to pick between futures vs forward, those contracts are futures as they are exchange traded and with a defined settlement structure. Inability to short has nothing to do with the contract itself genius, even if you have a regular es mini futures contract if your brokerage refuse to provide you margin you still cant short it, and if cme itself disables short selling you also cant. They did just that to the equity exchanges in the 08 crisis.
Why would I want to buy GHS a month or two ahead of time knowing that the spot price is trending downwards all the time?
because the spot is 0.01 and the settlement for those contracts are 0.008 and 0.004. 0.008 and 0.004 < 0.01 genius. It's a speculative play on future difficulty/hashrate, just like any other derivatives such as options.
Stop with this nonsense, it's like nails on chalkboard. Go argue about valuation instead, at least then noone will be able to point out how clueless you are, as your guess is as good as mine (well probably not..)