Well, this website https://usinterestrates.com/corporate-bond-yields says that currently, B-grade bonds go at around 8.5%. So bonds paying 10% would be below B, pretty much in junk bond territory https://www.investopedia.com/terms/j/junkbond.asp .

So maybe it's not high risk enough for you, but it is definitely high risk enough for the market.

But the best approach is just comparing rates. Go to https://archive.epa.gov/epawaste/nonhaz/municipal/web/pdf/bo... , and you will see a huge list of companies whose bonds are classified by armies of analysts as "less risky" than these 10% Anthropic bonds. Is Anthropic less risky than AT&T, or BP, or Firestone Tire & Rubber Co? The market says "no".

and you'd be thus mistaken

currently US long term bonds have very low yield and are being issued less as usual buyers move to gold/stock -- trust in US gov. has eroded especially in fiscal matters. The budget keeps growing, interest rates are still too low to combat inflation and debt is ever-expanding, without drastic measures taken to stabilize the situation: thus, high bond yield - we pay you premium to have at least someone buy it due to trustworthiness not being the sole attractor anymore