I was in a trail running club in that era and the organizer and a few others ran in flat Luna sandals. I will say that their form was beautiful - there’s no question in my mind that barefoot-inspired running produces a more natural locomotion.
But I tried it and it was a bust. A one mile run would lock my calf up, and that would set me back for weeks. I still have the Lunas and wear them on the boat.
Yeah if you’re already a competent runner using traditional shoes then switching to Lunas or similar will absolutely blast your calves if you try to maintain even a remotely similar pace or volume at the start.
I trail run and hike in my Chaco sandals. I need the arch support. I also wear socks when I do it because then small stones and rocks don't cause any issues.