[BUG] fsLR template description is (probably) inaccurate

[tsalo]

Describe your problem in detail.

bids-specification/src/schema/objects/enums.yaml

Lines 418 to 430 in 9377b20

	fsLR:
	value: fsLR
	display_name: fsLR
	description: |
	The `fsLR` is a **dual template** providing both volumetric and surface coordinates references.
	The volumetric template corresponds to `MNI152NLin6Asym`.
	Surface templates are given at several sampling densities:
	164k (used by HCP pipelines for 3T and 7T anatomical analysis),
	59k (used by HCP pipelines for 7T MRI bold and DWI analysis),
	32k (used by HCP pipelines for 3T MRI bold and DWI analysis), or
	4k (used by HCP pipelines for MEG analysis) fsaverage_LR surface reconstructed from the T1w image.
	Used by Freesurfer.

The fsLR template isn't actually a dual template. The combination of the fsLR surface with MNI152NLin6Asym volume is a convention, not a rule.

Describe what you expected.

fsLR should only describe the surface template. See #1900 for discussion of the distinction between the surface and volume templates in combined surface-volume files (i.e., CIFTIs).

BIDS specification section

https://bids-specification.readthedocs.io/en/stable/glossary.html#fslr-enums

https://bids-specification.readthedocs.io/en/stable/appendices/coordinate-systems.html#standard-template-identifiers

[tsalo]

From maintainers meeting today- folks are comfortable using fsLR as shorthand for fsLR+MNI152NLin6Asym. However, I still think we need to clarify that in the documentation, since a CIFTI with fsLR surfaces and some other volumetric space is still in fsLR (though one would need to differentiate it from standard fsLR), and that might not be clear from the description.