Fmriprep/nipype/niworkflow working directory behavior/clash

When running fmriprep, the default working directory is "$PWD/work". If I concurrently run fmriprep jobs on two different input BIDS directories, where some of the participant labels coincide, is it possible for contents of the working directories for two different fmriprep jobs to clash/conflict? Or does fmriprep/nipype/niworkflows handle this internally? E.g., is it necessary to structure as "$PWD/work/$(basename -- "$bids_dir")" (or otherwise different directories for each input) (run in the parent of the BIDS directories) to prevent clash in this situation.

(root) (parent of BIDS directories)