Not necessarily.
11 ng could definitely kill someone who had not used the drug before.
However, for experienced fentanyl users, the average fatal dose is about 24 ng.
However, fentanyl overdose almost always includes multiple drug use, so trying to tweeze out the exact fatal level of fentanyl is very difficult.
Also of interest...
Fentanyl is used by victims of very painful cancers, usually in the last few weeks of life, or earlier if opioid pain killers stop working.
Such victims are usually unconscious during their last few days of life, and their fentanyl blood level averages 12 ng, just 1 ng above George Floyd's tox screen.
In my opinion, the prosecution is going to need to prove in court that George Floyd was a chronic fentanyl user, or else the murder charge is not going to stick.
Another question, is foaming at the mouth normal for fentanyl / meth use or related to his heart condition?