> we know that somewhere between 25-50% of COVID-19 cases appear to be entirely asymptomatic (as opposed to pre-symptomatic).
Which is not a big number at all, at least, not big enough to suggest that infecting more people is a solution. Considering that the chances to have symptoms and die rise exponentially with age, the estimated 25-50% are young and lucky ones. Still, it is known that even kids (unlucky, i.e. not in great proportion) do die:
https://www.thesun.co.uk/news/11576622/uk-death-toll-rises-a...
"Six-week-old baby dies of coronavirus as UK death toll hits 31,241 after 626 more killed"
France, March:
https://www.france24.com/en/20200327-16-year-old-girl-become...
"16-year-old girl becomes France’s youngest coronavirus victim"
etc.
By the way, from the older investigations about how people self-report their respiratory illnesses, it is already known that some significant percentage would not report anything and when asked claim not to have any symptoms even when they demonstrably do have them.
Even now, in the middle of coronavirus pandemics, there are people who "become used" to less oxygen in their blood, and behave as "not ill" even as their body becomes permanently damaged by the low concentration of the oxygen destroying their tissues.
So "asymptomatic" in the sense "the patient or the person filling up the questionnaire didn't feel being ill" is totally different from "the doctors didn't find any symptoms."