[Issue]: Should axes restrictions inside multsicales also apply to scene coordinate systems?

Describe the issue

Currently the 0.6.dev3 spec has a bunch of restrictions on the coordinate systems inside multiscales:

https://ngff-spec.readthedocs.io/en/latest/#multiscales-metadata

The following MUST hold for all coordinate systems inside multiscales metadata. The length of axes must be between 2 and 5 and MUST be equal to the dimensionality of the Zarr arrays storing the image data (see datasets:path). The axes MUST contain 2 or 3 entries of type:space and MAY contain one additional entry of type:time and MAY contain one additional entry of type:channel or a null / custom type. In addition, the entries MUST be ordered by type where the time axis must come first (if present), followed by the channel or custom axis (if present) and the axes of type space. If there are three spatial axes where two correspond to the image plane (yx) and images are stacked along the other (anisotropic) axis (z), the spatial axes SHOULD be ordered as zyx. Each multiscales object MUST contain the field datasets, which is an array of objects describing the arrays storing the individual resolution levels. Each object in datasets MUST contain the field path, whose value is a string containing the path to the Zarr array for this resolution relative to the current Zarr group. The paths MUST be ordered from largest (i.e. highest resolution) to smallest. Every Zarr array referred to by a path MUST have the same number of dimensions and datatype, and MUST NOT have more than 5 dimensions. The number of dimensions and order MUST correspond to number and order of axes.

As far as I can see these restrictions don't also apply to coordinate systems defined inside scene objects. Is this a deliberate choice, or should the specification be updated so the same restrictions apply to all coordinate systems stored in OME-Zarr metdata?

Start with the multiscales metadata section in the linked 0.6.dev3 specification and compare its coordinate-system restrictions with the scene objects section. Determine whether the difference is deliberate, then document the decision and update the relevant specification text if needed. Done means the scope of these restrictions is unambiguous for all applicable coordinate systems.