If this is true (and remains true through to live), it marks a complete change of direction, where normally each MacOS upgrade is slower than the last, because of complexity. Years ago, I had reason to rebuild my old 2011 3.4GHz 27" iMac running High Sierra, having replaced its 1TB HDD with an SSD. Out of curiosity, I used its Restore option to install its original Snow Leopard OS just to see how it ran. How fast was it? F***ing rocket ship, that my current M1 Studio Max would have no hope of catching, because the Snow Leopard OS was so much simpler and less resource-intensive than High Sierra.