Now that 2D metadata doesn't exist, these separate store types are no longer necessary, we previously used
- ElementLinearData for "real" non-meta data
- FlatLinearData for a mix of ElementLinearData and MetaLinearData before they had been separated and aligned
- MetaLinearData for meta data
- LinearData to be a common parent of ElementLinearData and MetaLinearData
Now we no longer have MetaLinearData, both Flat* and Element* become redundant separations.