CAL
CALEDONIA MINING CORP PLC
stock TSE

Your math assumes that there current debt is at 0%, which would not be correct.
I've just picked an example - CA87971MAY99 - So you can look it up. It's a 400m telus bond at 4.75% coupon rate - matures in 2045. So you can see the differential based on your math is only 3.25%. Plus it matures in 2045.
From September 2023 more cently (I realize it's before the 30 year really spiked):\\
The 5.95% notes, Series CAL, were priced at $99.267 per $100 principal amount for an effective yield of 6.003% per annum until maturity, and will mature on September 8, 2053
I'm not disagreeing that higher interest rates affect higher debt level companies more, but it's important to be realistic on the effects rather than quick math.