It seems to me that all investments involve risk. What makes borrowing to invest in BTC any more risky than investing in a start-up, opening a business or buying a house (which may be full of defects, for example)? If the person's financial situation is stable and the banker, after studying the file in depth, is OK, I don't see why you can't borrow money to buy BTC. In fact, this is what some large companies do.
Yes, borrowing money to invest in Bitcoin is not a bad idea if someone has a stable financial situation and the bank agrees that loan. But I think will not be accurate when comparing investment in speculative assets with businesses, and thinking they have the same risk.
Business risks come from the market, management, strategies and finance...and if someone is smart and flexible, they can minimize business risks significantly. In other words, business risks can be controlled through plans and strategies. But investing in Bitcoin, risks such as price fluctuations, technology, and legality...are mainly out of our control. Therefore, in my opinion, investing in Bitcoin is more risky than businesses, but high risks may be highly profitable, so it will depend on each person's choice.