That article doesn't accurately summarize the state of the science nor the individual results it reports.
For instance, the Iceland study did not, contrary to the article, find a general prevalence of 13.3%. Rather, the 13.3% was for "targeted testing" (i.e., people with who were symptomatic, had recently traveled to high-risk countries, or had contact with infected persons). Thus, there is going to be a heavy selection bias for people who were more likely to test positive. The same paper also references a general population screening where between .6% and .8% tested positive (there were two general screenings, an open invitation portion and a random population portion). Spread of SARS-CoV-2 in the Icelandic Population
The California antibody tests it cites were pretty roundly criticized for flawed methodologies (self selection problems), mathematical errors, and for reliance on unreliable tests. Experts demolish studies suggesting COVID-19 is no worse than flu.
It also doesn't include New York's efforts, which indicated that the prevalence of the virus is under 13% for that heavily hit state. That also suggest an IFR floor for the state of ~1% (x10 regular flu) based on known NY deaths. (19.45 million * 12.3% = 2.39 million infected. Reported NY deaths were at 24,000 deaths on May 2nd when results announced, which, divided by 2.39 million = 1.00% CFR.) NY results