Rule 21350 only applies when the mapped compartments are the same dimensions, not if they are different (cf sbmlteam/libsbml#275).
The new rule should be:
"The value of the attribute \token{spatial:unitSize} on a \CompartmentMapping must have a value between 0 and 1, inclusive, when the dimensions of the referenced compartments have the same dimensions."
Rule 21350 only applies when the mapped compartments are the same dimensions, not if they are different (cf sbmlteam/libsbml#275).
The new rule should be:
"The value of the attribute \token{spatial:unitSize} on a \CompartmentMapping must have a value between 0 and 1, inclusive, when the dimensions of the referenced compartments have the same dimensions."