I am wondering what this new functionality has been designed for.

I imported a huge DWG in SW 2020 as a reference sketch.

First of all, I need to mention that SW 2020 crashed if AutoCAD blocks are not exploded. That does not happen in SW 2019.

Second, the import process is slower than in  SW 2019

Third, the zoom in/out experience is slower than in SW 2019. Also once you zoom a bit in, the whole sketch disappears. Update: It happens if Graphics Performance Pipeline Setting is checked.

Forth, if I press CTRL+Q (only one sketch in the feature tree), the rebuild takes 2 seconds in SW 2019 and it hangs SW 2020 (waiting for 10 minutes now).

Will document all these problems in SRs, but the question remain: "What problem are we trying to solve here?".