“Lost worlds” seems a bit sensational. They simply have developed a method that renders more detail and greater depth of tectonic movement. “Recent activity” is not defined here, but I’m fairly sure tectonic activity has been present throughout the planet’s history.
I saw a cool video on here once of the evolution of the earth. Looked like a slow motion exploding ball. Undulating, expanding and collapsing thru the eons. So certainly there are areas that once were on the surface that are buried now.
In geologic terms, ‘recent’ could be 100k years.................