No, I don’t think that that is correct. Or maybe I am misunderstanding you.
I think that a huge number of people had it, had little or now symptoms, >were not tested for it< and recovered and important! — were not counted in the statistics.
Here the way to look at it.
If 5 people out of 100 died then that is a 5% mortality rate. Where did the 100 of infected people number come from? From people who just so happens, happen chance?, were tested for it. Probably because the had symptoms and suspected that they might have it. Or other reasons.
Now, if that 100 number is actually 1000 or 900 people were exposed but weren’t tested then the mortality rate drops by 10.
The mortality rate becomes 0.5%. A significantly less number.
Maybe a huge number have had it, that would only mean its even more infectious that we currently think.
The fatality rate is based on confirmed case, not hypothetical guesses as to how many people might have COVID 19.