I think the feature is incomplete.
The only mention of it in the manual is a single paragraph.
From my testing, longer audio files will render to shorter phrases (which is counter intuitive)
The menu config Render Slice Options → Lines Per Beat will work only within the bounds set by the length of the audio file.
For example, here are a couple test cases:
CASE A:
Audio file length = 1 second
Render Slice Options → Lines Per Beat = 4
Output phrase resolution = 64 lines
CASE B:
Audio file length = 1 second
Render Slice Options → Lines Per Beat = 32
Output phrase resolution = 512 lines
CASE C:
Audio file length = 60 seconds
Render Slice Options → Lines Per Beat = 4
Output phrase resolution = 4 lines
CASE D:
Audio file length = 60 seconds
Render Slice Options → Lines Per Beat = 32
Output phrase resolution = 32 lines
Effectively, the only way to set the resolution of the rendered phrase is by setting the length of the input audio file. This is regardless of the number of slices.
It seems like the coding underlying the feature is incomplete.
Feature could be made much more powerful with additional config, such as the phrase’s resulting line resolution.
FYI
Oddly, the longer the file, the fewer lines rendered and vice versa.
A really short 1 second audio file renders to a phrase with 512 lines!