It's common knowledge that fentanyl causes more respiratory depression than morphine. But the first attached paper says otherwise.

The rates of respiratory depression, headache, confusion, agitation, and hallucination were not significantly different between the three opioids. The rate of respiratory depression between morphine, hydromorphone, and fentanyl was 8%, 7%, and 4%, respectively.

The therapeutic index of fentanyl is generally listed as being much higher than morphine, and alpha-methylfentanyl, "notorious" for being dangerous, has one very similar to that of morphine. Data on this is in the second attachment. Hopefully alpha-methylfentanyl is actually similarly safe to morphine in reality, as the duration is actually long enough to be useful recreationally, unlikely the regular fentanyls.

What's going on here?