There are several studies available specifically about myocarditis after the mRNA COVID vaccination. So it is not true that experts are making these statements without data, the data is here and I'll quote three different studies here:
From a Danish study on myocarditis after COVID vaccination
We observed no readmissions, diagnoses of heart failure, or deaths among people with myocarditis or myopericarditis occurring within 28 days of mRNA-1273 vaccination.
From a study in Israel
A total of 76% of cases of myocarditis were described as mild and 22% as intermediate; 1 case was associated with cardiogenic shock. After a median follow-up of 83 days after the onset of myocarditis, 1 patient had been readmitted to the hospital, and 1 had died of an unknown cause after discharge. Of 14 patients who had left ventricular dysfunction on echocardiography during admission, 10 still had such dysfunction at the time of hospital discharge. Of these patients, 5 underwent subsequent testing that revealed normal heart function.
From another study in Israel
In the 136 cases of definite or probable myocarditis, the clinical presentation in 129 was generally mild, with resolution of myocarditis in most cases, as judged by clinical symptoms and inflammatory markers and troponin elevation, electrocardiographic and echocardiographic normalization, and a relatively short length of hospital stay. However, one person with fulminant myocarditis died.
We have data on the severity of the rare myocarditis case after COVID vaccination, and that data indicates that it is mild in most cases. And the data in these studies would look pretty different if the death rate were 27% as alleged in the claim. There are only 2 deaths mentioned here, out of roughly 600 myocarditis cases, and one of them is listed as "unkown vause after discharge" so it is unclear if it is at all connected. This is very obviously not even close to the death rate mentioned on the podcast for myocarditis in general.
It is also important to keep in mind that overall the risk of myocarditis and pericarditis from COVID itself is higher than from the vaccine. Though there is a subset of the population (younger than 40 and with two doses of Moderna) where the risk from the vaccine is slightly higher. Keep in mind though that this comparison ignores all other complications from COVID, it does not compare the total risk. You can find all the details in the publication "Risks of myocarditis, pericarditis, and cardiac arrhythmias associated with COVID-19 vaccination or SARS-CoV-2 infection".