I will say these types are a risky play. The idea here is to grow faster in fiat terms than what you can get just holding bitcoin.

For example bitcoin is just under $2T in market cap. To go up 100% in fiat terms you need the market cap to go up to $4T meanwhile some miner only has a market cap of $200M as the price goes on the way to $4T that miner will catch a bit from investors looking for growth. This the market cap of the miner will be bid up to maybe $2B which crushed the bitcoin returns and then you can buy more bitcoin with the fiat gain.