The Scottish government did not accept that COVID was "here to stay", the UK COVID-19 inquiry has heard.
Mark Woolhouse, a professor of infectious disease epidemiology at the University of Edinburgh, told the inquiry politicians were "mistaken or misinformed" in their understanding of the virus, and said the public was "misled".
Responding to questions from Jamie Dawson KC, counsel to the inquiry, Mr Woolhouse said he "didn't understand the Scottish government's strategy over the summer of 2020".
He added: "The emphasis was on a very, very cautious relaxation from the lockdown.
"And it seemed to be important to the politicians that it was more cautious than the one in England, so they were emphasising that they didn't articulate in any way that I understood, what they thought the public health benefit of this caution actually would be given what we said about a second wave.
"And then this segued into this idea that actually the falling cases in Scotland would somehow continue, we could end up in zero COVID."
He added: "This was not consistent with the evidence that had been available since February 2020."
Outdoor arrests were 'utterly absurd'
The professor said the virus "transmits very poorly" outdoors, and said he regretted that many people were arrested for taking part in outdoor activities such as mountain climbing.
He said: "So there was pretty much zero public health benefit keeping us indoors. That wasn't required at all - we never needed to do that.
"There are caveats like if people are outdoors and being intimate, that's something. There was never any need for that."
Baroness Heather Hallett asked the professor to name outdoor activities that were deemed acceptable during lockdown.
He said: "You'd need to do a fairly detailed public health appraisal of where you drew the line.
"We, in the UK, arrested people for going on solo walks in the mountains. That is utterly absurd. That devalues the whole idea of social distancing, that anyone can see, this is nonsense."
He added: "Another good example that was an absolute outcry in the summer of 2020 was that people were going to beaches.
"There was never an outbreak of COVID anywhere in the world linked to a beach. It was fine. People could go to the beach, but nonetheless, were very resistant to that."
Lessons from schools and lockdown decisions
Mr Woolhouse said schools contributed "a little" to the spread of the virus, but said this was "so little, that there was essentially no danger" that schools would take the UK past the "tipping point".
He said that while he accepts closing schools was done as a precaution during the first lockdown, the UK government should have acted on evidence from around the world and taken a similar approach to Denmark, which reopened schools in May 2020.
The inquiry also heard from the professor that there was "very little consideration" for the mental health of the population by enforcing a stay-at-home order, but that was "fairly quickly recognised by the Scottish government".
He added: "There was a lot of concern about how well people would tolerate lockdown, but that was an unknown.
"I feel that discussion was more in the vein of, well, how long and severe a lockdown could we get away with that the public would tolerate, rather than actually looking at evidence of components of it and saying we didn't need them."
The inquiry continues.