Thanks, @dr460nf1r3 .
I notice also in this changelog that swappiness has been altered to use ZRAM. I assume this explains the default setting of 133. I've got lots of RAM, but also an ingrained horror from the early days of SSDs of seeing unnecessary write actions to disk. This is going to take some getting used to. 
Does this mean I should avoid (or approach differently) some of the other associated tweaks, such as vfs_cache_pressure, etc?