The 11.9 percent mentioned in your quote refers to probability of death for the population (i.e. a random person where the gender of the patient and the doctor is unknown).
The 12.4 percent refers to probability of death for a woman given a male doctor. If that is 12 percent higher, as the quote above says, then the probability of death for a woman given a female doctor is about 11.07%
So its an increase of 1.3 percentage points. The article kind of obfuscates that though.
Look at the map at the end. It clearly shows women being higher percentage in areas that have better mortality rates for heart disease which are both heavily influenced by access (response time) to medical care and other socioeconomic factors
this is not perfect, but it shows that other factors are probably more likely to be the reason other than jumping to conclusions about which sex is a better doctor.
https://www.kff.org/other/state-indicator/medical-school-gra...
I don't believe that many people are even suggesting this conclusion.
But the article[0], in PNAS, has confidence intervals.
Edit: The thing is that in the abstract no form of statistical indicator was reported. That plus its absence from the linked article means that unless someone here can get access to the paper our discussion is in vain.
It's kind of like complaining that you ordered 1 kg of water but were delivered 1 l, and insisting that everyone measure water by weight rather than volume. Don't read too much into that analogy, but the relationship between P values and confidence intervals is of a broadly similar nature.
Now you just have to look at group sizes, possible confounding factors, etc...