In parts of Australia there are designated "reference areas" which have a higher level of environmental protection than national parks. They are typically remote areas that humans do not visit and have not historically and directly disturbed. These areas are also typically less disturbed by other external factors such as seeding of non-endemic species by birds. Scientists use such areas as a reference to what other less protected areas of the environment would have looked like before human impact. In scientific journals you'll find surveys of such reference areas including the prevalence of different taxon, as well as surveys of national parks or other areas being compared.

I've tried to find similar for Finland. The closest I've found is [1] which maps "old forests" which are defined to be over 100 years old (not actually very old). The three examples [2], [3] and [4] are Google street view imagery of nearby "old forests" and all indicate a much higher biodiversity and natural planting than the site Google has cleared. The site Google has cleared and nearby forests are visible in overhead imagery as having a pattern of tree plantings (distinct rows/grid) and show visible disturbance for forestry trails (ground compaction), whereas the "old forest" sites don't have these patterns. The "old forest" sites also show variance in trunk diameters, greater separation between trunks, more forest floor diversity and more tree variety (both taxon and structure). Plantation forests have trees deliberately planted too close to each other to encourage upright growth habit, lower limbs are deliberately removed and trees thinned after some years, all to maximise the number of sawmill-ready trunks. Revegetation planting would look completely different to what occurred at the Google site.

Revegetation planting and ongoing management is also much more expensive to do correctly. It's a struggle to find success stories. Best examples likely involve aerial seeding and complex seed collection and preparation, as well as ongoing manual weed management and introduced species control for 20+ years. There is often a fair bit of complexity to simulating nature to make seeds viable--for example, refer to Przewalski's Horse case study where hoofed animals were reintroduced and found to be essential for embedding seeds at required depth and reshaping the terrain to support seed germination. More examples are water courses upstream having to be cleared of weeds first, introduced animals need to be excluded/culled, etc, etc.

[1] https://luontovahti.fi/vanhojametsia -- select Pohjois-Pohjanmaa as the area then zoom in near Muhos.

[2] https://maps.app.goo.gl/wncKi2JMxuPXC7Bc7

[3] https://maps.app.goo.gl/BX2ta5dQmihSgVAM6

[4] https://maps.app.goo.gl/4W3WvR5tH9wroVna7