Scientists (which Tegnell is, effectively) are not meant to be politicians, and them getting into political matters is an excellent way to corrupt science. Although Sweden is not a place where one would look to think of corruption, there are still serious ethical issues with this. This is also a form of experimentation in COVID-19 that is among the riskiest and most dangerous in the world.
Early on in the COVID-19 pandemic, the significant differences in death rates in developed countries for COVID-19 were attributed mostly to whether COVID-19 severely penetrated care homes, mostly designed for the elderly. We know that Sweden did not have proper PPE protection in these care homes to protect their most vulnerable, and it still does not. Sure, the death rates worldwide have been going down, at least in developed countries, because, perhaps we have become smarter at treating it, despite having no effective treatment for it.
Still, it is not prudent to expose people needlessly to a virus that we know is deadly--and we know little about. A lot of these deaths could have been prevented, with relatively little pain, although it takes a lot of sacrifice.
One of the countries I am sovereign to, Croatia, (the other being the USA) has not had any COVID-19 cases for 3 days in a row [1]. You know, a former war-torn Yugoslav country that is up and rising and just became part of the EU in 2013. This kind of stuff is not rocket science. Even war-torn, economically suffering countries can be successful at these sorts of endeavors. It just requires brave political leaders (along with a strong emphasis on public health--which a lot of ex-Yugoslav countries actually have) who can deal with crises (which Croatia has legitimately dealt with before).