Wrong the rule of thumb in slim mode

[likemusic]

According to the docs:

The rule of thumb in slim mode is as follows: use the size of the PBF file you are trying to import or about 75% of RAM, whatever is smaller.

But in fact seems that cache size must be above twice lager then source file.
I've made tests on 2 pbf-files and it shown that for cache size equal to source file size import speed for ways just 30-40% from max possible.

Google sheet with tests results.