The likely explanations are fairly benign: Flu vaccine deaths are undercounted because people die all the time for lots of reasons and no-one bothered to check for a connection between the death and the vaccine. Covid vaccine deaths are overcounted because we live in a Covid obsessed world and any death that can be traced to a possible Covid exposure or the vaccine is a Covid/vaccine death even if the person dies from other causes. Many people who received the Covid vaccine are in the highest risk groups for any disease (i.e., old, fat, or sedentary, with underlying health issues) and are more likely to die or have a stroke or heart attack even if they never received the Covid vaccine.
To put things in perspective, the daily death rate in the United States for all causes is .0087, which means that your chances of dying on any given day for any reason is more than twice as high as your chances of dying from the Covid vaccine.
The simple reporting bias you point out in post 20, could account for a few thousand, or a few tens of thousands of VAERS reports, out of over a quarter of a billion vaccine doses already administered in the USA.
Everyone is highly focused on COVID and its vaccines, whereas people tend to dismiss the significance of flu shots.