Buying mining equipment has two components - choosing and operating hardware, and speculating on the future of price/difficulty ratio.
Having these two components as a bundle is inefficient.
Mining bonds allow each component to be carried out most efficiently - one side buys bonds thus investing in the concept of mining profitability without having to physically operate hardware, and the other side uses the money to buy equipment without taking speculative risk.
The OP is right. You are making the mistake that he pointed out. It looks like he has facts on his side. These instruments may be efficient (for the seller??) but that does not make them BONDS. A bond has a specific meaning, and no matter how many times it is used wrong, that does not make it right.
I am not commenting on the usefulness of the instruments, just the terminology. They are not bonds. Calling them such makes them sound much safer then they really are.
Are BTC-denominated bonds with a specified BTC face value and returns "safe"? No, because BTC itself is highly speculative, volatile, and could crash any minute. Mining bonds have a fixed face value and return denominated in MH/s, which is also speculative.
From Wikipedia: