Passing in precomputed brain mask affects T1 preprocessing in fMRIPrep

Summary of what happened:

For my dataset I have found that ANTspyNET consistently produces a good/clean brain mask compared to fmriprep (antsBrainExtraction x Freesurfeer method). The default fmriprep method often outputs brain mask/segmentations that include the skull/non-brain tissues. As a result, I have been feeding my ANTspyNET mask as input via the --derivatives flag. While this works and the resulting outputs look good (see attached screenshots: decent tissue segmentations, good BOLD-T1 coreg etc), I noticed that the preprocessed anatomical T1 gets skull stripped in the process. Is this a sign of something going wrong under the hood?

Would greatly appreciate your thoughts, thank you!

Command used (and if a helper script was used, a link to the helper script or the command generated):

CMD="apptainer run --cleanenv \
      -B /path_to_multiband_rsfMRI_data:/data \
      ${CONTAINER} \
      /data/Outputs/BIDS \
      /data/Outputs/fmriprep \
      participant \
      --participant-label 01 \
      --session-label 01 \
      --fs-license-file /data/Software/license.txt \
      --force no-bbr \
      --ignore slicetiming \
      --output-spaces func anat MNI152NLin2009cAsym:res-native \
      --skull-strip-t1w skip \
      --derivatives fmriprep=/data/Outputs/fmriprep \
      --use-syn-sdc \
      -w /data/Outputs/fmriprep -vvv"

Version:

25.2.3

Environment (Docker, Singularity / Apptainer, custom installation):

Apptainer

Data formatted according to a validatable standard? Please provide the output of the validator:

251125-09:27:55,505 cli INFO:
	 Telemetry system to collect crashes and errors is enabled - thanks for your feedback!. Use option ``--notrack`` to opt out.
251125-09:27:59,596 cli DEBUG:
	 Initializing BIDS Layout
251125-09:28:45,171 nipype.workflow IMPORTANT:
	 Running fMRIPrep version 25.2.3

         License NOTICE ##################################################
         fMRIPrep 25.2.3
         Copyright The NiPreps Developers.