Interestingly, this is apparently a widely-held misconception and the swappiness value doesn’t map directly to a percentage. It’s actually more complicated than that:
So, a default of 10 is actually far too low, especially with ZRAM being available. I’ve been running with swappiness=133 specifically to make the kernel actively use the available ZRAM (or ZSWAP in my case).
There’s some more explanation here: