[phylo] small refactorings to make `toSeriesOfClustering` more readable

4 jobs for 494-dev-phylo-hh-mm-ss-2 in 55 minutes and 27 seconds (queued for 4 seconds)
Status Job ID Name Coverage
  Cabal
passed #19126
cabal

00:26:16

 
  Stack
passed #19127
stack

00:03:24

 
  Bench
manual #19128
allowed to fail manual
bench
 
  Test
passed #19129
test

00:25:47